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abd4349ff9
As Steven suggested [1], we should access the pointers from the trace event to avoid dereferencing them to the tracepoint function when the tracepoint is disabled. [1] https://lkml.org/lkml/2021/11/3/409 Link: https://lkml.kernel.org/r/4cd393b4d57f8f01ed72c001509b28e3a3b1a8c1.1646985115.git.baolin.wang@linux.alibaba.com Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Steven Rostedt (Google) <rostedt@goodmis.org> Cc: Ingo Molnar <mingo@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
3093 lines
85 KiB
C
3093 lines
85 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* linux/mm/compaction.c
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*
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* Memory compaction for the reduction of external fragmentation. Note that
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* this heavily depends upon page migration to do all the real heavy
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* lifting
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*
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* Copyright IBM Corp. 2007-2010 Mel Gorman <mel@csn.ul.ie>
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*/
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#include <linux/cpu.h>
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#include <linux/swap.h>
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#include <linux/migrate.h>
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#include <linux/compaction.h>
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#include <linux/mm_inline.h>
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#include <linux/sched/signal.h>
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#include <linux/backing-dev.h>
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#include <linux/sysctl.h>
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#include <linux/sysfs.h>
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#include <linux/page-isolation.h>
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#include <linux/kasan.h>
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#include <linux/kthread.h>
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#include <linux/freezer.h>
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#include <linux/page_owner.h>
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#include <linux/psi.h>
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#include "internal.h"
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#ifdef CONFIG_COMPACTION
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static inline void count_compact_event(enum vm_event_item item)
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{
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count_vm_event(item);
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}
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static inline void count_compact_events(enum vm_event_item item, long delta)
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{
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count_vm_events(item, delta);
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}
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#else
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#define count_compact_event(item) do { } while (0)
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#define count_compact_events(item, delta) do { } while (0)
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#endif
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#if defined CONFIG_COMPACTION || defined CONFIG_CMA
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#define CREATE_TRACE_POINTS
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#include <trace/events/compaction.h>
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#define block_start_pfn(pfn, order) round_down(pfn, 1UL << (order))
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#define block_end_pfn(pfn, order) ALIGN((pfn) + 1, 1UL << (order))
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#define pageblock_start_pfn(pfn) block_start_pfn(pfn, pageblock_order)
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#define pageblock_end_pfn(pfn) block_end_pfn(pfn, pageblock_order)
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/*
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* Fragmentation score check interval for proactive compaction purposes.
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*/
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static const unsigned int HPAGE_FRAG_CHECK_INTERVAL_MSEC = 500;
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/*
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* Page order with-respect-to which proactive compaction
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* calculates external fragmentation, which is used as
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* the "fragmentation score" of a node/zone.
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*/
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#if defined CONFIG_TRANSPARENT_HUGEPAGE
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#define COMPACTION_HPAGE_ORDER HPAGE_PMD_ORDER
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#elif defined CONFIG_HUGETLBFS
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#define COMPACTION_HPAGE_ORDER HUGETLB_PAGE_ORDER
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#else
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#define COMPACTION_HPAGE_ORDER (PMD_SHIFT - PAGE_SHIFT)
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#endif
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static unsigned long release_freepages(struct list_head *freelist)
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{
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struct page *page, *next;
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unsigned long high_pfn = 0;
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list_for_each_entry_safe(page, next, freelist, lru) {
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unsigned long pfn = page_to_pfn(page);
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list_del(&page->lru);
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__free_page(page);
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if (pfn > high_pfn)
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high_pfn = pfn;
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}
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return high_pfn;
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}
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static void split_map_pages(struct list_head *list)
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{
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unsigned int i, order, nr_pages;
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struct page *page, *next;
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LIST_HEAD(tmp_list);
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list_for_each_entry_safe(page, next, list, lru) {
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list_del(&page->lru);
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order = page_private(page);
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nr_pages = 1 << order;
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post_alloc_hook(page, order, __GFP_MOVABLE);
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if (order)
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split_page(page, order);
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for (i = 0; i < nr_pages; i++) {
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list_add(&page->lru, &tmp_list);
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page++;
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}
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}
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list_splice(&tmp_list, list);
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}
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#ifdef CONFIG_COMPACTION
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int PageMovable(struct page *page)
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{
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struct address_space *mapping;
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VM_BUG_ON_PAGE(!PageLocked(page), page);
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if (!__PageMovable(page))
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return 0;
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mapping = page_mapping(page);
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if (mapping && mapping->a_ops && mapping->a_ops->isolate_page)
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return 1;
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return 0;
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}
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EXPORT_SYMBOL(PageMovable);
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void __SetPageMovable(struct page *page, struct address_space *mapping)
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{
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VM_BUG_ON_PAGE(!PageLocked(page), page);
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VM_BUG_ON_PAGE((unsigned long)mapping & PAGE_MAPPING_MOVABLE, page);
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page->mapping = (void *)((unsigned long)mapping | PAGE_MAPPING_MOVABLE);
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}
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EXPORT_SYMBOL(__SetPageMovable);
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void __ClearPageMovable(struct page *page)
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{
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VM_BUG_ON_PAGE(!PageMovable(page), page);
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/*
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* Clear registered address_space val with keeping PAGE_MAPPING_MOVABLE
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* flag so that VM can catch up released page by driver after isolation.
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* With it, VM migration doesn't try to put it back.
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*/
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page->mapping = (void *)((unsigned long)page->mapping &
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PAGE_MAPPING_MOVABLE);
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}
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EXPORT_SYMBOL(__ClearPageMovable);
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/* Do not skip compaction more than 64 times */
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#define COMPACT_MAX_DEFER_SHIFT 6
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/*
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* Compaction is deferred when compaction fails to result in a page
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* allocation success. 1 << compact_defer_shift, compactions are skipped up
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* to a limit of 1 << COMPACT_MAX_DEFER_SHIFT
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*/
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static void defer_compaction(struct zone *zone, int order)
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{
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zone->compact_considered = 0;
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zone->compact_defer_shift++;
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if (order < zone->compact_order_failed)
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zone->compact_order_failed = order;
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if (zone->compact_defer_shift > COMPACT_MAX_DEFER_SHIFT)
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zone->compact_defer_shift = COMPACT_MAX_DEFER_SHIFT;
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trace_mm_compaction_defer_compaction(zone, order);
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}
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/* Returns true if compaction should be skipped this time */
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static bool compaction_deferred(struct zone *zone, int order)
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{
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unsigned long defer_limit = 1UL << zone->compact_defer_shift;
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if (order < zone->compact_order_failed)
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return false;
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/* Avoid possible overflow */
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if (++zone->compact_considered >= defer_limit) {
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zone->compact_considered = defer_limit;
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return false;
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}
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trace_mm_compaction_deferred(zone, order);
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return true;
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}
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/*
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* Update defer tracking counters after successful compaction of given order,
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* which means an allocation either succeeded (alloc_success == true) or is
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* expected to succeed.
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*/
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void compaction_defer_reset(struct zone *zone, int order,
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bool alloc_success)
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{
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if (alloc_success) {
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zone->compact_considered = 0;
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zone->compact_defer_shift = 0;
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}
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if (order >= zone->compact_order_failed)
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zone->compact_order_failed = order + 1;
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trace_mm_compaction_defer_reset(zone, order);
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}
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/* Returns true if restarting compaction after many failures */
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static bool compaction_restarting(struct zone *zone, int order)
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{
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if (order < zone->compact_order_failed)
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return false;
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return zone->compact_defer_shift == COMPACT_MAX_DEFER_SHIFT &&
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zone->compact_considered >= 1UL << zone->compact_defer_shift;
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}
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/* Returns true if the pageblock should be scanned for pages to isolate. */
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static inline bool isolation_suitable(struct compact_control *cc,
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struct page *page)
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{
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if (cc->ignore_skip_hint)
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return true;
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return !get_pageblock_skip(page);
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}
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static void reset_cached_positions(struct zone *zone)
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{
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zone->compact_cached_migrate_pfn[0] = zone->zone_start_pfn;
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zone->compact_cached_migrate_pfn[1] = zone->zone_start_pfn;
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zone->compact_cached_free_pfn =
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pageblock_start_pfn(zone_end_pfn(zone) - 1);
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}
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/*
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* Compound pages of >= pageblock_order should consistently be skipped until
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* released. It is always pointless to compact pages of such order (if they are
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* migratable), and the pageblocks they occupy cannot contain any free pages.
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*/
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static bool pageblock_skip_persistent(struct page *page)
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{
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if (!PageCompound(page))
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return false;
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page = compound_head(page);
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if (compound_order(page) >= pageblock_order)
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return true;
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return false;
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}
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static bool
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__reset_isolation_pfn(struct zone *zone, unsigned long pfn, bool check_source,
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bool check_target)
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{
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struct page *page = pfn_to_online_page(pfn);
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struct page *block_page;
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struct page *end_page;
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unsigned long block_pfn;
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if (!page)
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return false;
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if (zone != page_zone(page))
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return false;
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if (pageblock_skip_persistent(page))
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return false;
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/*
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* If skip is already cleared do no further checking once the
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* restart points have been set.
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*/
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if (check_source && check_target && !get_pageblock_skip(page))
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return true;
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/*
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* If clearing skip for the target scanner, do not select a
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* non-movable pageblock as the starting point.
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*/
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if (!check_source && check_target &&
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get_pageblock_migratetype(page) != MIGRATE_MOVABLE)
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return false;
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/* Ensure the start of the pageblock or zone is online and valid */
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block_pfn = pageblock_start_pfn(pfn);
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block_pfn = max(block_pfn, zone->zone_start_pfn);
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block_page = pfn_to_online_page(block_pfn);
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if (block_page) {
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page = block_page;
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pfn = block_pfn;
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}
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/* Ensure the end of the pageblock or zone is online and valid */
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block_pfn = pageblock_end_pfn(pfn) - 1;
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block_pfn = min(block_pfn, zone_end_pfn(zone) - 1);
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end_page = pfn_to_online_page(block_pfn);
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if (!end_page)
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return false;
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/*
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* Only clear the hint if a sample indicates there is either a
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* free page or an LRU page in the block. One or other condition
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* is necessary for the block to be a migration source/target.
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*/
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do {
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if (check_source && PageLRU(page)) {
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clear_pageblock_skip(page);
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return true;
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}
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if (check_target && PageBuddy(page)) {
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clear_pageblock_skip(page);
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return true;
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}
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page += (1 << PAGE_ALLOC_COSTLY_ORDER);
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pfn += (1 << PAGE_ALLOC_COSTLY_ORDER);
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} while (page <= end_page);
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return false;
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}
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/*
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* This function is called to clear all cached information on pageblocks that
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* should be skipped for page isolation when the migrate and free page scanner
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* meet.
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*/
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static void __reset_isolation_suitable(struct zone *zone)
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{
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unsigned long migrate_pfn = zone->zone_start_pfn;
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unsigned long free_pfn = zone_end_pfn(zone) - 1;
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unsigned long reset_migrate = free_pfn;
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unsigned long reset_free = migrate_pfn;
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bool source_set = false;
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bool free_set = false;
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if (!zone->compact_blockskip_flush)
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return;
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zone->compact_blockskip_flush = false;
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/*
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* Walk the zone and update pageblock skip information. Source looks
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* for PageLRU while target looks for PageBuddy. When the scanner
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* is found, both PageBuddy and PageLRU are checked as the pageblock
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* is suitable as both source and target.
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*/
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for (; migrate_pfn < free_pfn; migrate_pfn += pageblock_nr_pages,
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free_pfn -= pageblock_nr_pages) {
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cond_resched();
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/* Update the migrate PFN */
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if (__reset_isolation_pfn(zone, migrate_pfn, true, source_set) &&
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migrate_pfn < reset_migrate) {
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source_set = true;
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reset_migrate = migrate_pfn;
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zone->compact_init_migrate_pfn = reset_migrate;
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zone->compact_cached_migrate_pfn[0] = reset_migrate;
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zone->compact_cached_migrate_pfn[1] = reset_migrate;
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}
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/* Update the free PFN */
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if (__reset_isolation_pfn(zone, free_pfn, free_set, true) &&
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free_pfn > reset_free) {
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free_set = true;
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reset_free = free_pfn;
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zone->compact_init_free_pfn = reset_free;
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zone->compact_cached_free_pfn = reset_free;
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}
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}
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/* Leave no distance if no suitable block was reset */
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if (reset_migrate >= reset_free) {
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zone->compact_cached_migrate_pfn[0] = migrate_pfn;
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zone->compact_cached_migrate_pfn[1] = migrate_pfn;
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zone->compact_cached_free_pfn = free_pfn;
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}
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}
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void reset_isolation_suitable(pg_data_t *pgdat)
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{
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int zoneid;
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for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
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struct zone *zone = &pgdat->node_zones[zoneid];
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if (!populated_zone(zone))
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continue;
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/* Only flush if a full compaction finished recently */
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if (zone->compact_blockskip_flush)
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__reset_isolation_suitable(zone);
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}
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}
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/*
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* Sets the pageblock skip bit if it was clear. Note that this is a hint as
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* locks are not required for read/writers. Returns true if it was already set.
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*/
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static bool test_and_set_skip(struct compact_control *cc, struct page *page,
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unsigned long pfn)
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{
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bool skip;
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/* Do no update if skip hint is being ignored */
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if (cc->ignore_skip_hint)
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return false;
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if (!IS_ALIGNED(pfn, pageblock_nr_pages))
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return false;
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skip = get_pageblock_skip(page);
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if (!skip && !cc->no_set_skip_hint)
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set_pageblock_skip(page);
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return skip;
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}
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static void update_cached_migrate(struct compact_control *cc, unsigned long pfn)
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{
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struct zone *zone = cc->zone;
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pfn = pageblock_end_pfn(pfn);
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/* Set for isolation rather than compaction */
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if (cc->no_set_skip_hint)
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return;
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if (pfn > zone->compact_cached_migrate_pfn[0])
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zone->compact_cached_migrate_pfn[0] = pfn;
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if (cc->mode != MIGRATE_ASYNC &&
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pfn > zone->compact_cached_migrate_pfn[1])
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zone->compact_cached_migrate_pfn[1] = pfn;
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}
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/*
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* If no pages were isolated then mark this pageblock to be skipped in the
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* future. The information is later cleared by __reset_isolation_suitable().
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*/
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static void update_pageblock_skip(struct compact_control *cc,
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struct page *page, unsigned long pfn)
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{
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struct zone *zone = cc->zone;
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if (cc->no_set_skip_hint)
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return;
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if (!page)
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return;
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set_pageblock_skip(page);
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/* Update where async and sync compaction should restart */
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if (pfn < zone->compact_cached_free_pfn)
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zone->compact_cached_free_pfn = pfn;
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}
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#else
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static inline bool isolation_suitable(struct compact_control *cc,
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struct page *page)
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{
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return true;
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}
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static inline bool pageblock_skip_persistent(struct page *page)
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{
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return false;
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}
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static inline void update_pageblock_skip(struct compact_control *cc,
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struct page *page, unsigned long pfn)
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{
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}
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static void update_cached_migrate(struct compact_control *cc, unsigned long pfn)
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{
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}
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static bool test_and_set_skip(struct compact_control *cc, struct page *page,
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unsigned long pfn)
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{
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return false;
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}
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#endif /* CONFIG_COMPACTION */
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/*
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* Compaction requires the taking of some coarse locks that are potentially
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* very heavily contended. For async compaction, trylock and record if the
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* lock is contended. The lock will still be acquired but compaction will
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* abort when the current block is finished regardless of success rate.
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* Sync compaction acquires the lock.
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*
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* Always returns true which makes it easier to track lock state in callers.
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*/
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static bool compact_lock_irqsave(spinlock_t *lock, unsigned long *flags,
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struct compact_control *cc)
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__acquires(lock)
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{
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/* Track if the lock is contended in async mode */
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if (cc->mode == MIGRATE_ASYNC && !cc->contended) {
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if (spin_trylock_irqsave(lock, *flags))
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return true;
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cc->contended = true;
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}
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spin_lock_irqsave(lock, *flags);
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return true;
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}
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/*
|
|
* Compaction requires the taking of some coarse locks that are potentially
|
|
* very heavily contended. The lock should be periodically unlocked to avoid
|
|
* having disabled IRQs for a long time, even when there is nobody waiting on
|
|
* the lock. It might also be that allowing the IRQs will result in
|
|
* need_resched() becoming true. If scheduling is needed, async compaction
|
|
* aborts. Sync compaction schedules.
|
|
* Either compaction type will also abort if a fatal signal is pending.
|
|
* In either case if the lock was locked, it is dropped and not regained.
|
|
*
|
|
* Returns true if compaction should abort due to fatal signal pending, or
|
|
* async compaction due to need_resched()
|
|
* Returns false when compaction can continue (sync compaction might have
|
|
* scheduled)
|
|
*/
|
|
static bool compact_unlock_should_abort(spinlock_t *lock,
|
|
unsigned long flags, bool *locked, struct compact_control *cc)
|
|
{
|
|
if (*locked) {
|
|
spin_unlock_irqrestore(lock, flags);
|
|
*locked = false;
|
|
}
|
|
|
|
if (fatal_signal_pending(current)) {
|
|
cc->contended = true;
|
|
return true;
|
|
}
|
|
|
|
cond_resched();
|
|
|
|
return false;
|
|
}
|
|
|
|
/*
|
|
* Isolate free pages onto a private freelist. If @strict is true, will abort
|
|
* returning 0 on any invalid PFNs or non-free pages inside of the pageblock
|
|
* (even though it may still end up isolating some pages).
|
|
*/
|
|
static unsigned long isolate_freepages_block(struct compact_control *cc,
|
|
unsigned long *start_pfn,
|
|
unsigned long end_pfn,
|
|
struct list_head *freelist,
|
|
unsigned int stride,
|
|
bool strict)
|
|
{
|
|
int nr_scanned = 0, total_isolated = 0;
|
|
struct page *cursor;
|
|
unsigned long flags = 0;
|
|
bool locked = false;
|
|
unsigned long blockpfn = *start_pfn;
|
|
unsigned int order;
|
|
|
|
/* Strict mode is for isolation, speed is secondary */
|
|
if (strict)
|
|
stride = 1;
|
|
|
|
cursor = pfn_to_page(blockpfn);
|
|
|
|
/* Isolate free pages. */
|
|
for (; blockpfn < end_pfn; blockpfn += stride, cursor += stride) {
|
|
int isolated;
|
|
struct page *page = cursor;
|
|
|
|
/*
|
|
* Periodically drop the lock (if held) regardless of its
|
|
* contention, to give chance to IRQs. Abort if fatal signal
|
|
* pending or async compaction detects need_resched()
|
|
*/
|
|
if (!(blockpfn % SWAP_CLUSTER_MAX)
|
|
&& compact_unlock_should_abort(&cc->zone->lock, flags,
|
|
&locked, cc))
|
|
break;
|
|
|
|
nr_scanned++;
|
|
|
|
/*
|
|
* For compound pages such as THP and hugetlbfs, we can save
|
|
* potentially a lot of iterations if we skip them at once.
|
|
* The check is racy, but we can consider only valid values
|
|
* and the only danger is skipping too much.
|
|
*/
|
|
if (PageCompound(page)) {
|
|
const unsigned int order = compound_order(page);
|
|
|
|
if (likely(order < MAX_ORDER)) {
|
|
blockpfn += (1UL << order) - 1;
|
|
cursor += (1UL << order) - 1;
|
|
}
|
|
goto isolate_fail;
|
|
}
|
|
|
|
if (!PageBuddy(page))
|
|
goto isolate_fail;
|
|
|
|
/*
|
|
* If we already hold the lock, we can skip some rechecking.
|
|
* Note that if we hold the lock now, checked_pageblock was
|
|
* already set in some previous iteration (or strict is true),
|
|
* so it is correct to skip the suitable migration target
|
|
* recheck as well.
|
|
*/
|
|
if (!locked) {
|
|
locked = compact_lock_irqsave(&cc->zone->lock,
|
|
&flags, cc);
|
|
|
|
/* Recheck this is a buddy page under lock */
|
|
if (!PageBuddy(page))
|
|
goto isolate_fail;
|
|
}
|
|
|
|
/* Found a free page, will break it into order-0 pages */
|
|
order = buddy_order(page);
|
|
isolated = __isolate_free_page(page, order);
|
|
if (!isolated)
|
|
break;
|
|
set_page_private(page, order);
|
|
|
|
total_isolated += isolated;
|
|
cc->nr_freepages += isolated;
|
|
list_add_tail(&page->lru, freelist);
|
|
|
|
if (!strict && cc->nr_migratepages <= cc->nr_freepages) {
|
|
blockpfn += isolated;
|
|
break;
|
|
}
|
|
/* Advance to the end of split page */
|
|
blockpfn += isolated - 1;
|
|
cursor += isolated - 1;
|
|
continue;
|
|
|
|
isolate_fail:
|
|
if (strict)
|
|
break;
|
|
else
|
|
continue;
|
|
|
|
}
|
|
|
|
if (locked)
|
|
spin_unlock_irqrestore(&cc->zone->lock, flags);
|
|
|
|
/*
|
|
* There is a tiny chance that we have read bogus compound_order(),
|
|
* so be careful to not go outside of the pageblock.
|
|
*/
|
|
if (unlikely(blockpfn > end_pfn))
|
|
blockpfn = end_pfn;
|
|
|
|
trace_mm_compaction_isolate_freepages(*start_pfn, blockpfn,
|
|
nr_scanned, total_isolated);
|
|
|
|
/* Record how far we have got within the block */
|
|
*start_pfn = blockpfn;
|
|
|
|
/*
|
|
* If strict isolation is requested by CMA then check that all the
|
|
* pages requested were isolated. If there were any failures, 0 is
|
|
* returned and CMA will fail.
|
|
*/
|
|
if (strict && blockpfn < end_pfn)
|
|
total_isolated = 0;
|
|
|
|
cc->total_free_scanned += nr_scanned;
|
|
if (total_isolated)
|
|
count_compact_events(COMPACTISOLATED, total_isolated);
|
|
return total_isolated;
|
|
}
|
|
|
|
/**
|
|
* isolate_freepages_range() - isolate free pages.
|
|
* @cc: Compaction control structure.
|
|
* @start_pfn: The first PFN to start isolating.
|
|
* @end_pfn: The one-past-last PFN.
|
|
*
|
|
* Non-free pages, invalid PFNs, or zone boundaries within the
|
|
* [start_pfn, end_pfn) range are considered errors, cause function to
|
|
* undo its actions and return zero.
|
|
*
|
|
* Otherwise, function returns one-past-the-last PFN of isolated page
|
|
* (which may be greater then end_pfn if end fell in a middle of
|
|
* a free page).
|
|
*/
|
|
unsigned long
|
|
isolate_freepages_range(struct compact_control *cc,
|
|
unsigned long start_pfn, unsigned long end_pfn)
|
|
{
|
|
unsigned long isolated, pfn, block_start_pfn, block_end_pfn;
|
|
LIST_HEAD(freelist);
|
|
|
|
pfn = start_pfn;
|
|
block_start_pfn = pageblock_start_pfn(pfn);
|
|
if (block_start_pfn < cc->zone->zone_start_pfn)
|
|
block_start_pfn = cc->zone->zone_start_pfn;
|
|
block_end_pfn = pageblock_end_pfn(pfn);
|
|
|
|
for (; pfn < end_pfn; pfn += isolated,
|
|
block_start_pfn = block_end_pfn,
|
|
block_end_pfn += pageblock_nr_pages) {
|
|
/* Protect pfn from changing by isolate_freepages_block */
|
|
unsigned long isolate_start_pfn = pfn;
|
|
|
|
block_end_pfn = min(block_end_pfn, end_pfn);
|
|
|
|
/*
|
|
* pfn could pass the block_end_pfn if isolated freepage
|
|
* is more than pageblock order. In this case, we adjust
|
|
* scanning range to right one.
|
|
*/
|
|
if (pfn >= block_end_pfn) {
|
|
block_start_pfn = pageblock_start_pfn(pfn);
|
|
block_end_pfn = pageblock_end_pfn(pfn);
|
|
block_end_pfn = min(block_end_pfn, end_pfn);
|
|
}
|
|
|
|
if (!pageblock_pfn_to_page(block_start_pfn,
|
|
block_end_pfn, cc->zone))
|
|
break;
|
|
|
|
isolated = isolate_freepages_block(cc, &isolate_start_pfn,
|
|
block_end_pfn, &freelist, 0, true);
|
|
|
|
/*
|
|
* In strict mode, isolate_freepages_block() returns 0 if
|
|
* there are any holes in the block (ie. invalid PFNs or
|
|
* non-free pages).
|
|
*/
|
|
if (!isolated)
|
|
break;
|
|
|
|
/*
|
|
* If we managed to isolate pages, it is always (1 << n) *
|
|
* pageblock_nr_pages for some non-negative n. (Max order
|
|
* page may span two pageblocks).
|
|
*/
|
|
}
|
|
|
|
/* __isolate_free_page() does not map the pages */
|
|
split_map_pages(&freelist);
|
|
|
|
if (pfn < end_pfn) {
|
|
/* Loop terminated early, cleanup. */
|
|
release_freepages(&freelist);
|
|
return 0;
|
|
}
|
|
|
|
/* We don't use freelists for anything. */
|
|
return pfn;
|
|
}
|
|
|
|
/* Similar to reclaim, but different enough that they don't share logic */
|
|
static bool too_many_isolated(pg_data_t *pgdat)
|
|
{
|
|
bool too_many;
|
|
|
|
unsigned long active, inactive, isolated;
|
|
|
|
inactive = node_page_state(pgdat, NR_INACTIVE_FILE) +
|
|
node_page_state(pgdat, NR_INACTIVE_ANON);
|
|
active = node_page_state(pgdat, NR_ACTIVE_FILE) +
|
|
node_page_state(pgdat, NR_ACTIVE_ANON);
|
|
isolated = node_page_state(pgdat, NR_ISOLATED_FILE) +
|
|
node_page_state(pgdat, NR_ISOLATED_ANON);
|
|
|
|
too_many = isolated > (inactive + active) / 2;
|
|
if (!too_many)
|
|
wake_throttle_isolated(pgdat);
|
|
|
|
return too_many;
|
|
}
|
|
|
|
/**
|
|
* isolate_migratepages_block() - isolate all migrate-able pages within
|
|
* a single pageblock
|
|
* @cc: Compaction control structure.
|
|
* @low_pfn: The first PFN to isolate
|
|
* @end_pfn: The one-past-the-last PFN to isolate, within same pageblock
|
|
* @mode: Isolation mode to be used.
|
|
*
|
|
* Isolate all pages that can be migrated from the range specified by
|
|
* [low_pfn, end_pfn). The range is expected to be within same pageblock.
|
|
* Returns errno, like -EAGAIN or -EINTR in case e.g signal pending or congestion,
|
|
* -ENOMEM in case we could not allocate a page, or 0.
|
|
* cc->migrate_pfn will contain the next pfn to scan.
|
|
*
|
|
* The pages are isolated on cc->migratepages list (not required to be empty),
|
|
* and cc->nr_migratepages is updated accordingly.
|
|
*/
|
|
static int
|
|
isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
|
|
unsigned long end_pfn, isolate_mode_t mode)
|
|
{
|
|
pg_data_t *pgdat = cc->zone->zone_pgdat;
|
|
unsigned long nr_scanned = 0, nr_isolated = 0;
|
|
struct lruvec *lruvec;
|
|
unsigned long flags = 0;
|
|
struct lruvec *locked = NULL;
|
|
struct page *page = NULL, *valid_page = NULL;
|
|
struct address_space *mapping;
|
|
unsigned long start_pfn = low_pfn;
|
|
bool skip_on_failure = false;
|
|
unsigned long next_skip_pfn = 0;
|
|
bool skip_updated = false;
|
|
int ret = 0;
|
|
|
|
cc->migrate_pfn = low_pfn;
|
|
|
|
/*
|
|
* Ensure that there are not too many pages isolated from the LRU
|
|
* list by either parallel reclaimers or compaction. If there are,
|
|
* delay for some time until fewer pages are isolated
|
|
*/
|
|
while (unlikely(too_many_isolated(pgdat))) {
|
|
/* stop isolation if there are still pages not migrated */
|
|
if (cc->nr_migratepages)
|
|
return -EAGAIN;
|
|
|
|
/* async migration should just abort */
|
|
if (cc->mode == MIGRATE_ASYNC)
|
|
return -EAGAIN;
|
|
|
|
reclaim_throttle(pgdat, VMSCAN_THROTTLE_ISOLATED);
|
|
|
|
if (fatal_signal_pending(current))
|
|
return -EINTR;
|
|
}
|
|
|
|
cond_resched();
|
|
|
|
if (cc->direct_compaction && (cc->mode == MIGRATE_ASYNC)) {
|
|
skip_on_failure = true;
|
|
next_skip_pfn = block_end_pfn(low_pfn, cc->order);
|
|
}
|
|
|
|
/* Time to isolate some pages for migration */
|
|
for (; low_pfn < end_pfn; low_pfn++) {
|
|
|
|
if (skip_on_failure && low_pfn >= next_skip_pfn) {
|
|
/*
|
|
* We have isolated all migration candidates in the
|
|
* previous order-aligned block, and did not skip it due
|
|
* to failure. We should migrate the pages now and
|
|
* hopefully succeed compaction.
|
|
*/
|
|
if (nr_isolated)
|
|
break;
|
|
|
|
/*
|
|
* We failed to isolate in the previous order-aligned
|
|
* block. Set the new boundary to the end of the
|
|
* current block. Note we can't simply increase
|
|
* next_skip_pfn by 1 << order, as low_pfn might have
|
|
* been incremented by a higher number due to skipping
|
|
* a compound or a high-order buddy page in the
|
|
* previous loop iteration.
|
|
*/
|
|
next_skip_pfn = block_end_pfn(low_pfn, cc->order);
|
|
}
|
|
|
|
/*
|
|
* Periodically drop the lock (if held) regardless of its
|
|
* contention, to give chance to IRQs. Abort completely if
|
|
* a fatal signal is pending.
|
|
*/
|
|
if (!(low_pfn % SWAP_CLUSTER_MAX)) {
|
|
if (locked) {
|
|
unlock_page_lruvec_irqrestore(locked, flags);
|
|
locked = NULL;
|
|
}
|
|
|
|
if (fatal_signal_pending(current)) {
|
|
cc->contended = true;
|
|
ret = -EINTR;
|
|
|
|
goto fatal_pending;
|
|
}
|
|
|
|
cond_resched();
|
|
}
|
|
|
|
nr_scanned++;
|
|
|
|
page = pfn_to_page(low_pfn);
|
|
|
|
/*
|
|
* Check if the pageblock has already been marked skipped.
|
|
* Only the aligned PFN is checked as the caller isolates
|
|
* COMPACT_CLUSTER_MAX at a time so the second call must
|
|
* not falsely conclude that the block should be skipped.
|
|
*/
|
|
if (!valid_page && IS_ALIGNED(low_pfn, pageblock_nr_pages)) {
|
|
if (!cc->ignore_skip_hint && get_pageblock_skip(page)) {
|
|
low_pfn = end_pfn;
|
|
page = NULL;
|
|
goto isolate_abort;
|
|
}
|
|
valid_page = page;
|
|
}
|
|
|
|
if (PageHuge(page) && cc->alloc_contig) {
|
|
ret = isolate_or_dissolve_huge_page(page, &cc->migratepages);
|
|
|
|
/*
|
|
* Fail isolation in case isolate_or_dissolve_huge_page()
|
|
* reports an error. In case of -ENOMEM, abort right away.
|
|
*/
|
|
if (ret < 0) {
|
|
/* Do not report -EBUSY down the chain */
|
|
if (ret == -EBUSY)
|
|
ret = 0;
|
|
low_pfn += (1UL << compound_order(page)) - 1;
|
|
goto isolate_fail;
|
|
}
|
|
|
|
if (PageHuge(page)) {
|
|
/*
|
|
* Hugepage was successfully isolated and placed
|
|
* on the cc->migratepages list.
|
|
*/
|
|
low_pfn += compound_nr(page) - 1;
|
|
goto isolate_success_no_list;
|
|
}
|
|
|
|
/*
|
|
* Ok, the hugepage was dissolved. Now these pages are
|
|
* Buddy and cannot be re-allocated because they are
|
|
* isolated. Fall-through as the check below handles
|
|
* Buddy pages.
|
|
*/
|
|
}
|
|
|
|
/*
|
|
* Skip if free. We read page order here without zone lock
|
|
* which is generally unsafe, but the race window is small and
|
|
* the worst thing that can happen is that we skip some
|
|
* potential isolation targets.
|
|
*/
|
|
if (PageBuddy(page)) {
|
|
unsigned long freepage_order = buddy_order_unsafe(page);
|
|
|
|
/*
|
|
* Without lock, we cannot be sure that what we got is
|
|
* a valid page order. Consider only values in the
|
|
* valid order range to prevent low_pfn overflow.
|
|
*/
|
|
if (freepage_order > 0 && freepage_order < MAX_ORDER)
|
|
low_pfn += (1UL << freepage_order) - 1;
|
|
continue;
|
|
}
|
|
|
|
/*
|
|
* Regardless of being on LRU, compound pages such as THP and
|
|
* hugetlbfs are not to be compacted unless we are attempting
|
|
* an allocation much larger than the huge page size (eg CMA).
|
|
* We can potentially save a lot of iterations if we skip them
|
|
* at once. The check is racy, but we can consider only valid
|
|
* values and the only danger is skipping too much.
|
|
*/
|
|
if (PageCompound(page) && !cc->alloc_contig) {
|
|
const unsigned int order = compound_order(page);
|
|
|
|
if (likely(order < MAX_ORDER))
|
|
low_pfn += (1UL << order) - 1;
|
|
goto isolate_fail;
|
|
}
|
|
|
|
/*
|
|
* Check may be lockless but that's ok as we recheck later.
|
|
* It's possible to migrate LRU and non-lru movable pages.
|
|
* Skip any other type of page
|
|
*/
|
|
if (!PageLRU(page)) {
|
|
/*
|
|
* __PageMovable can return false positive so we need
|
|
* to verify it under page_lock.
|
|
*/
|
|
if (unlikely(__PageMovable(page)) &&
|
|
!PageIsolated(page)) {
|
|
if (locked) {
|
|
unlock_page_lruvec_irqrestore(locked, flags);
|
|
locked = NULL;
|
|
}
|
|
|
|
if (!isolate_movable_page(page, mode))
|
|
goto isolate_success;
|
|
}
|
|
|
|
goto isolate_fail;
|
|
}
|
|
|
|
/*
|
|
* Migration will fail if an anonymous page is pinned in memory,
|
|
* so avoid taking lru_lock and isolating it unnecessarily in an
|
|
* admittedly racy check.
|
|
*/
|
|
mapping = page_mapping(page);
|
|
if (!mapping && page_count(page) > page_mapcount(page))
|
|
goto isolate_fail;
|
|
|
|
/*
|
|
* Only allow to migrate anonymous pages in GFP_NOFS context
|
|
* because those do not depend on fs locks.
|
|
*/
|
|
if (!(cc->gfp_mask & __GFP_FS) && mapping)
|
|
goto isolate_fail;
|
|
|
|
/*
|
|
* Be careful not to clear PageLRU until after we're
|
|
* sure the page is not being freed elsewhere -- the
|
|
* page release code relies on it.
|
|
*/
|
|
if (unlikely(!get_page_unless_zero(page)))
|
|
goto isolate_fail;
|
|
|
|
/* Only take pages on LRU: a check now makes later tests safe */
|
|
if (!PageLRU(page))
|
|
goto isolate_fail_put;
|
|
|
|
/* Compaction might skip unevictable pages but CMA takes them */
|
|
if (!(mode & ISOLATE_UNEVICTABLE) && PageUnevictable(page))
|
|
goto isolate_fail_put;
|
|
|
|
/*
|
|
* To minimise LRU disruption, the caller can indicate with
|
|
* ISOLATE_ASYNC_MIGRATE that it only wants to isolate pages
|
|
* it will be able to migrate without blocking - clean pages
|
|
* for the most part. PageWriteback would require blocking.
|
|
*/
|
|
if ((mode & ISOLATE_ASYNC_MIGRATE) && PageWriteback(page))
|
|
goto isolate_fail_put;
|
|
|
|
if ((mode & ISOLATE_ASYNC_MIGRATE) && PageDirty(page)) {
|
|
bool migrate_dirty;
|
|
|
|
/*
|
|
* Only pages without mappings or that have a
|
|
* ->migratepage callback are possible to migrate
|
|
* without blocking. However, we can be racing with
|
|
* truncation so it's necessary to lock the page
|
|
* to stabilise the mapping as truncation holds
|
|
* the page lock until after the page is removed
|
|
* from the page cache.
|
|
*/
|
|
if (!trylock_page(page))
|
|
goto isolate_fail_put;
|
|
|
|
mapping = page_mapping(page);
|
|
migrate_dirty = !mapping || mapping->a_ops->migratepage;
|
|
unlock_page(page);
|
|
if (!migrate_dirty)
|
|
goto isolate_fail_put;
|
|
}
|
|
|
|
/* Try isolate the page */
|
|
if (!TestClearPageLRU(page))
|
|
goto isolate_fail_put;
|
|
|
|
lruvec = folio_lruvec(page_folio(page));
|
|
|
|
/* If we already hold the lock, we can skip some rechecking */
|
|
if (lruvec != locked) {
|
|
if (locked)
|
|
unlock_page_lruvec_irqrestore(locked, flags);
|
|
|
|
compact_lock_irqsave(&lruvec->lru_lock, &flags, cc);
|
|
locked = lruvec;
|
|
|
|
lruvec_memcg_debug(lruvec, page_folio(page));
|
|
|
|
/* Try get exclusive access under lock */
|
|
if (!skip_updated) {
|
|
skip_updated = true;
|
|
if (test_and_set_skip(cc, page, low_pfn))
|
|
goto isolate_abort;
|
|
}
|
|
|
|
/*
|
|
* Page become compound since the non-locked check,
|
|
* and it's on LRU. It can only be a THP so the order
|
|
* is safe to read and it's 0 for tail pages.
|
|
*/
|
|
if (unlikely(PageCompound(page) && !cc->alloc_contig)) {
|
|
low_pfn += compound_nr(page) - 1;
|
|
SetPageLRU(page);
|
|
goto isolate_fail_put;
|
|
}
|
|
}
|
|
|
|
/* The whole page is taken off the LRU; skip the tail pages. */
|
|
if (PageCompound(page))
|
|
low_pfn += compound_nr(page) - 1;
|
|
|
|
/* Successfully isolated */
|
|
del_page_from_lru_list(page, lruvec);
|
|
mod_node_page_state(page_pgdat(page),
|
|
NR_ISOLATED_ANON + page_is_file_lru(page),
|
|
thp_nr_pages(page));
|
|
|
|
isolate_success:
|
|
list_add(&page->lru, &cc->migratepages);
|
|
isolate_success_no_list:
|
|
cc->nr_migratepages += compound_nr(page);
|
|
nr_isolated += compound_nr(page);
|
|
|
|
/*
|
|
* Avoid isolating too much unless this block is being
|
|
* rescanned (e.g. dirty/writeback pages, parallel allocation)
|
|
* or a lock is contended. For contention, isolate quickly to
|
|
* potentially remove one source of contention.
|
|
*/
|
|
if (cc->nr_migratepages >= COMPACT_CLUSTER_MAX &&
|
|
!cc->rescan && !cc->contended) {
|
|
++low_pfn;
|
|
break;
|
|
}
|
|
|
|
continue;
|
|
|
|
isolate_fail_put:
|
|
/* Avoid potential deadlock in freeing page under lru_lock */
|
|
if (locked) {
|
|
unlock_page_lruvec_irqrestore(locked, flags);
|
|
locked = NULL;
|
|
}
|
|
put_page(page);
|
|
|
|
isolate_fail:
|
|
if (!skip_on_failure && ret != -ENOMEM)
|
|
continue;
|
|
|
|
/*
|
|
* We have isolated some pages, but then failed. Release them
|
|
* instead of migrating, as we cannot form the cc->order buddy
|
|
* page anyway.
|
|
*/
|
|
if (nr_isolated) {
|
|
if (locked) {
|
|
unlock_page_lruvec_irqrestore(locked, flags);
|
|
locked = NULL;
|
|
}
|
|
putback_movable_pages(&cc->migratepages);
|
|
cc->nr_migratepages = 0;
|
|
nr_isolated = 0;
|
|
}
|
|
|
|
if (low_pfn < next_skip_pfn) {
|
|
low_pfn = next_skip_pfn - 1;
|
|
/*
|
|
* The check near the loop beginning would have updated
|
|
* next_skip_pfn too, but this is a bit simpler.
|
|
*/
|
|
next_skip_pfn += 1UL << cc->order;
|
|
}
|
|
|
|
if (ret == -ENOMEM)
|
|
break;
|
|
}
|
|
|
|
/*
|
|
* The PageBuddy() check could have potentially brought us outside
|
|
* the range to be scanned.
|
|
*/
|
|
if (unlikely(low_pfn > end_pfn))
|
|
low_pfn = end_pfn;
|
|
|
|
page = NULL;
|
|
|
|
isolate_abort:
|
|
if (locked)
|
|
unlock_page_lruvec_irqrestore(locked, flags);
|
|
if (page) {
|
|
SetPageLRU(page);
|
|
put_page(page);
|
|
}
|
|
|
|
/*
|
|
* Updated the cached scanner pfn once the pageblock has been scanned
|
|
* Pages will either be migrated in which case there is no point
|
|
* scanning in the near future or migration failed in which case the
|
|
* failure reason may persist. The block is marked for skipping if
|
|
* there were no pages isolated in the block or if the block is
|
|
* rescanned twice in a row.
|
|
*/
|
|
if (low_pfn == end_pfn && (!nr_isolated || cc->rescan)) {
|
|
if (valid_page && !skip_updated)
|
|
set_pageblock_skip(valid_page);
|
|
update_cached_migrate(cc, low_pfn);
|
|
}
|
|
|
|
trace_mm_compaction_isolate_migratepages(start_pfn, low_pfn,
|
|
nr_scanned, nr_isolated);
|
|
|
|
fatal_pending:
|
|
cc->total_migrate_scanned += nr_scanned;
|
|
if (nr_isolated)
|
|
count_compact_events(COMPACTISOLATED, nr_isolated);
|
|
|
|
cc->migrate_pfn = low_pfn;
|
|
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* isolate_migratepages_range() - isolate migrate-able pages in a PFN range
|
|
* @cc: Compaction control structure.
|
|
* @start_pfn: The first PFN to start isolating.
|
|
* @end_pfn: The one-past-last PFN.
|
|
*
|
|
* Returns -EAGAIN when contented, -EINTR in case of a signal pending, -ENOMEM
|
|
* in case we could not allocate a page, or 0.
|
|
*/
|
|
int
|
|
isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn,
|
|
unsigned long end_pfn)
|
|
{
|
|
unsigned long pfn, block_start_pfn, block_end_pfn;
|
|
int ret = 0;
|
|
|
|
/* Scan block by block. First and last block may be incomplete */
|
|
pfn = start_pfn;
|
|
block_start_pfn = pageblock_start_pfn(pfn);
|
|
if (block_start_pfn < cc->zone->zone_start_pfn)
|
|
block_start_pfn = cc->zone->zone_start_pfn;
|
|
block_end_pfn = pageblock_end_pfn(pfn);
|
|
|
|
for (; pfn < end_pfn; pfn = block_end_pfn,
|
|
block_start_pfn = block_end_pfn,
|
|
block_end_pfn += pageblock_nr_pages) {
|
|
|
|
block_end_pfn = min(block_end_pfn, end_pfn);
|
|
|
|
if (!pageblock_pfn_to_page(block_start_pfn,
|
|
block_end_pfn, cc->zone))
|
|
continue;
|
|
|
|
ret = isolate_migratepages_block(cc, pfn, block_end_pfn,
|
|
ISOLATE_UNEVICTABLE);
|
|
|
|
if (ret)
|
|
break;
|
|
|
|
if (cc->nr_migratepages >= COMPACT_CLUSTER_MAX)
|
|
break;
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
|
|
#endif /* CONFIG_COMPACTION || CONFIG_CMA */
|
|
#ifdef CONFIG_COMPACTION
|
|
|
|
static bool suitable_migration_source(struct compact_control *cc,
|
|
struct page *page)
|
|
{
|
|
int block_mt;
|
|
|
|
if (pageblock_skip_persistent(page))
|
|
return false;
|
|
|
|
if ((cc->mode != MIGRATE_ASYNC) || !cc->direct_compaction)
|
|
return true;
|
|
|
|
block_mt = get_pageblock_migratetype(page);
|
|
|
|
if (cc->migratetype == MIGRATE_MOVABLE)
|
|
return is_migrate_movable(block_mt);
|
|
else
|
|
return block_mt == cc->migratetype;
|
|
}
|
|
|
|
/* Returns true if the page is within a block suitable for migration to */
|
|
static bool suitable_migration_target(struct compact_control *cc,
|
|
struct page *page)
|
|
{
|
|
/* If the page is a large free page, then disallow migration */
|
|
if (PageBuddy(page)) {
|
|
/*
|
|
* We are checking page_order without zone->lock taken. But
|
|
* the only small danger is that we skip a potentially suitable
|
|
* pageblock, so it's not worth to check order for valid range.
|
|
*/
|
|
if (buddy_order_unsafe(page) >= pageblock_order)
|
|
return false;
|
|
}
|
|
|
|
if (cc->ignore_block_suitable)
|
|
return true;
|
|
|
|
/* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
|
|
if (is_migrate_movable(get_pageblock_migratetype(page)))
|
|
return true;
|
|
|
|
/* Otherwise skip the block */
|
|
return false;
|
|
}
|
|
|
|
static inline unsigned int
|
|
freelist_scan_limit(struct compact_control *cc)
|
|
{
|
|
unsigned short shift = BITS_PER_LONG - 1;
|
|
|
|
return (COMPACT_CLUSTER_MAX >> min(shift, cc->fast_search_fail)) + 1;
|
|
}
|
|
|
|
/*
|
|
* Test whether the free scanner has reached the same or lower pageblock than
|
|
* the migration scanner, and compaction should thus terminate.
|
|
*/
|
|
static inline bool compact_scanners_met(struct compact_control *cc)
|
|
{
|
|
return (cc->free_pfn >> pageblock_order)
|
|
<= (cc->migrate_pfn >> pageblock_order);
|
|
}
|
|
|
|
/*
|
|
* Used when scanning for a suitable migration target which scans freelists
|
|
* in reverse. Reorders the list such as the unscanned pages are scanned
|
|
* first on the next iteration of the free scanner
|
|
*/
|
|
static void
|
|
move_freelist_head(struct list_head *freelist, struct page *freepage)
|
|
{
|
|
LIST_HEAD(sublist);
|
|
|
|
if (!list_is_last(freelist, &freepage->lru)) {
|
|
list_cut_before(&sublist, freelist, &freepage->lru);
|
|
list_splice_tail(&sublist, freelist);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Similar to move_freelist_head except used by the migration scanner
|
|
* when scanning forward. It's possible for these list operations to
|
|
* move against each other if they search the free list exactly in
|
|
* lockstep.
|
|
*/
|
|
static void
|
|
move_freelist_tail(struct list_head *freelist, struct page *freepage)
|
|
{
|
|
LIST_HEAD(sublist);
|
|
|
|
if (!list_is_first(freelist, &freepage->lru)) {
|
|
list_cut_position(&sublist, freelist, &freepage->lru);
|
|
list_splice_tail(&sublist, freelist);
|
|
}
|
|
}
|
|
|
|
static void
|
|
fast_isolate_around(struct compact_control *cc, unsigned long pfn, unsigned long nr_isolated)
|
|
{
|
|
unsigned long start_pfn, end_pfn;
|
|
struct page *page;
|
|
|
|
/* Do not search around if there are enough pages already */
|
|
if (cc->nr_freepages >= cc->nr_migratepages)
|
|
return;
|
|
|
|
/* Minimise scanning during async compaction */
|
|
if (cc->direct_compaction && cc->mode == MIGRATE_ASYNC)
|
|
return;
|
|
|
|
/* Pageblock boundaries */
|
|
start_pfn = max(pageblock_start_pfn(pfn), cc->zone->zone_start_pfn);
|
|
end_pfn = min(pageblock_end_pfn(pfn), zone_end_pfn(cc->zone));
|
|
|
|
page = pageblock_pfn_to_page(start_pfn, end_pfn, cc->zone);
|
|
if (!page)
|
|
return;
|
|
|
|
/* Scan before */
|
|
if (start_pfn != pfn) {
|
|
isolate_freepages_block(cc, &start_pfn, pfn, &cc->freepages, 1, false);
|
|
if (cc->nr_freepages >= cc->nr_migratepages)
|
|
return;
|
|
}
|
|
|
|
/* Scan after */
|
|
start_pfn = pfn + nr_isolated;
|
|
if (start_pfn < end_pfn)
|
|
isolate_freepages_block(cc, &start_pfn, end_pfn, &cc->freepages, 1, false);
|
|
|
|
/* Skip this pageblock in the future as it's full or nearly full */
|
|
if (cc->nr_freepages < cc->nr_migratepages)
|
|
set_pageblock_skip(page);
|
|
}
|
|
|
|
/* Search orders in round-robin fashion */
|
|
static int next_search_order(struct compact_control *cc, int order)
|
|
{
|
|
order--;
|
|
if (order < 0)
|
|
order = cc->order - 1;
|
|
|
|
/* Search wrapped around? */
|
|
if (order == cc->search_order) {
|
|
cc->search_order--;
|
|
if (cc->search_order < 0)
|
|
cc->search_order = cc->order - 1;
|
|
return -1;
|
|
}
|
|
|
|
return order;
|
|
}
|
|
|
|
static unsigned long
|
|
fast_isolate_freepages(struct compact_control *cc)
|
|
{
|
|
unsigned int limit = max(1U, freelist_scan_limit(cc) >> 1);
|
|
unsigned int nr_scanned = 0;
|
|
unsigned long low_pfn, min_pfn, highest = 0;
|
|
unsigned long nr_isolated = 0;
|
|
unsigned long distance;
|
|
struct page *page = NULL;
|
|
bool scan_start = false;
|
|
int order;
|
|
|
|
/* Full compaction passes in a negative order */
|
|
if (cc->order <= 0)
|
|
return cc->free_pfn;
|
|
|
|
/*
|
|
* If starting the scan, use a deeper search and use the highest
|
|
* PFN found if a suitable one is not found.
|
|
*/
|
|
if (cc->free_pfn >= cc->zone->compact_init_free_pfn) {
|
|
limit = pageblock_nr_pages >> 1;
|
|
scan_start = true;
|
|
}
|
|
|
|
/*
|
|
* Preferred point is in the top quarter of the scan space but take
|
|
* a pfn from the top half if the search is problematic.
|
|
*/
|
|
distance = (cc->free_pfn - cc->migrate_pfn);
|
|
low_pfn = pageblock_start_pfn(cc->free_pfn - (distance >> 2));
|
|
min_pfn = pageblock_start_pfn(cc->free_pfn - (distance >> 1));
|
|
|
|
if (WARN_ON_ONCE(min_pfn > low_pfn))
|
|
low_pfn = min_pfn;
|
|
|
|
/*
|
|
* Search starts from the last successful isolation order or the next
|
|
* order to search after a previous failure
|
|
*/
|
|
cc->search_order = min_t(unsigned int, cc->order - 1, cc->search_order);
|
|
|
|
for (order = cc->search_order;
|
|
!page && order >= 0;
|
|
order = next_search_order(cc, order)) {
|
|
struct free_area *area = &cc->zone->free_area[order];
|
|
struct list_head *freelist;
|
|
struct page *freepage;
|
|
unsigned long flags;
|
|
unsigned int order_scanned = 0;
|
|
unsigned long high_pfn = 0;
|
|
|
|
if (!area->nr_free)
|
|
continue;
|
|
|
|
spin_lock_irqsave(&cc->zone->lock, flags);
|
|
freelist = &area->free_list[MIGRATE_MOVABLE];
|
|
list_for_each_entry_reverse(freepage, freelist, lru) {
|
|
unsigned long pfn;
|
|
|
|
order_scanned++;
|
|
nr_scanned++;
|
|
pfn = page_to_pfn(freepage);
|
|
|
|
if (pfn >= highest)
|
|
highest = max(pageblock_start_pfn(pfn),
|
|
cc->zone->zone_start_pfn);
|
|
|
|
if (pfn >= low_pfn) {
|
|
cc->fast_search_fail = 0;
|
|
cc->search_order = order;
|
|
page = freepage;
|
|
break;
|
|
}
|
|
|
|
if (pfn >= min_pfn && pfn > high_pfn) {
|
|
high_pfn = pfn;
|
|
|
|
/* Shorten the scan if a candidate is found */
|
|
limit >>= 1;
|
|
}
|
|
|
|
if (order_scanned >= limit)
|
|
break;
|
|
}
|
|
|
|
/* Use a minimum pfn if a preferred one was not found */
|
|
if (!page && high_pfn) {
|
|
page = pfn_to_page(high_pfn);
|
|
|
|
/* Update freepage for the list reorder below */
|
|
freepage = page;
|
|
}
|
|
|
|
/* Reorder to so a future search skips recent pages */
|
|
move_freelist_head(freelist, freepage);
|
|
|
|
/* Isolate the page if available */
|
|
if (page) {
|
|
if (__isolate_free_page(page, order)) {
|
|
set_page_private(page, order);
|
|
nr_isolated = 1 << order;
|
|
cc->nr_freepages += nr_isolated;
|
|
list_add_tail(&page->lru, &cc->freepages);
|
|
count_compact_events(COMPACTISOLATED, nr_isolated);
|
|
} else {
|
|
/* If isolation fails, abort the search */
|
|
order = cc->search_order + 1;
|
|
page = NULL;
|
|
}
|
|
}
|
|
|
|
spin_unlock_irqrestore(&cc->zone->lock, flags);
|
|
|
|
/*
|
|
* Smaller scan on next order so the total scan is related
|
|
* to freelist_scan_limit.
|
|
*/
|
|
if (order_scanned >= limit)
|
|
limit = max(1U, limit >> 1);
|
|
}
|
|
|
|
if (!page) {
|
|
cc->fast_search_fail++;
|
|
if (scan_start) {
|
|
/*
|
|
* Use the highest PFN found above min. If one was
|
|
* not found, be pessimistic for direct compaction
|
|
* and use the min mark.
|
|
*/
|
|
if (highest) {
|
|
page = pfn_to_page(highest);
|
|
cc->free_pfn = highest;
|
|
} else {
|
|
if (cc->direct_compaction && pfn_valid(min_pfn)) {
|
|
page = pageblock_pfn_to_page(min_pfn,
|
|
min(pageblock_end_pfn(min_pfn),
|
|
zone_end_pfn(cc->zone)),
|
|
cc->zone);
|
|
cc->free_pfn = min_pfn;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
if (highest && highest >= cc->zone->compact_cached_free_pfn) {
|
|
highest -= pageblock_nr_pages;
|
|
cc->zone->compact_cached_free_pfn = highest;
|
|
}
|
|
|
|
cc->total_free_scanned += nr_scanned;
|
|
if (!page)
|
|
return cc->free_pfn;
|
|
|
|
low_pfn = page_to_pfn(page);
|
|
fast_isolate_around(cc, low_pfn, nr_isolated);
|
|
return low_pfn;
|
|
}
|
|
|
|
/*
|
|
* Based on information in the current compact_control, find blocks
|
|
* suitable for isolating free pages from and then isolate them.
|
|
*/
|
|
static void isolate_freepages(struct compact_control *cc)
|
|
{
|
|
struct zone *zone = cc->zone;
|
|
struct page *page;
|
|
unsigned long block_start_pfn; /* start of current pageblock */
|
|
unsigned long isolate_start_pfn; /* exact pfn we start at */
|
|
unsigned long block_end_pfn; /* end of current pageblock */
|
|
unsigned long low_pfn; /* lowest pfn scanner is able to scan */
|
|
struct list_head *freelist = &cc->freepages;
|
|
unsigned int stride;
|
|
|
|
/* Try a small search of the free lists for a candidate */
|
|
isolate_start_pfn = fast_isolate_freepages(cc);
|
|
if (cc->nr_freepages)
|
|
goto splitmap;
|
|
|
|
/*
|
|
* Initialise the free scanner. The starting point is where we last
|
|
* successfully isolated from, zone-cached value, or the end of the
|
|
* zone when isolating for the first time. For looping we also need
|
|
* this pfn aligned down to the pageblock boundary, because we do
|
|
* block_start_pfn -= pageblock_nr_pages in the for loop.
|
|
* For ending point, take care when isolating in last pageblock of a
|
|
* zone which ends in the middle of a pageblock.
|
|
* The low boundary is the end of the pageblock the migration scanner
|
|
* is using.
|
|
*/
|
|
isolate_start_pfn = cc->free_pfn;
|
|
block_start_pfn = pageblock_start_pfn(isolate_start_pfn);
|
|
block_end_pfn = min(block_start_pfn + pageblock_nr_pages,
|
|
zone_end_pfn(zone));
|
|
low_pfn = pageblock_end_pfn(cc->migrate_pfn);
|
|
stride = cc->mode == MIGRATE_ASYNC ? COMPACT_CLUSTER_MAX : 1;
|
|
|
|
/*
|
|
* Isolate free pages until enough are available to migrate the
|
|
* pages on cc->migratepages. We stop searching if the migrate
|
|
* and free page scanners meet or enough free pages are isolated.
|
|
*/
|
|
for (; block_start_pfn >= low_pfn;
|
|
block_end_pfn = block_start_pfn,
|
|
block_start_pfn -= pageblock_nr_pages,
|
|
isolate_start_pfn = block_start_pfn) {
|
|
unsigned long nr_isolated;
|
|
|
|
/*
|
|
* This can iterate a massively long zone without finding any
|
|
* suitable migration targets, so periodically check resched.
|
|
*/
|
|
if (!(block_start_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages)))
|
|
cond_resched();
|
|
|
|
page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn,
|
|
zone);
|
|
if (!page)
|
|
continue;
|
|
|
|
/* Check the block is suitable for migration */
|
|
if (!suitable_migration_target(cc, page))
|
|
continue;
|
|
|
|
/* If isolation recently failed, do not retry */
|
|
if (!isolation_suitable(cc, page))
|
|
continue;
|
|
|
|
/* Found a block suitable for isolating free pages from. */
|
|
nr_isolated = isolate_freepages_block(cc, &isolate_start_pfn,
|
|
block_end_pfn, freelist, stride, false);
|
|
|
|
/* Update the skip hint if the full pageblock was scanned */
|
|
if (isolate_start_pfn == block_end_pfn)
|
|
update_pageblock_skip(cc, page, block_start_pfn);
|
|
|
|
/* Are enough freepages isolated? */
|
|
if (cc->nr_freepages >= cc->nr_migratepages) {
|
|
if (isolate_start_pfn >= block_end_pfn) {
|
|
/*
|
|
* Restart at previous pageblock if more
|
|
* freepages can be isolated next time.
|
|
*/
|
|
isolate_start_pfn =
|
|
block_start_pfn - pageblock_nr_pages;
|
|
}
|
|
break;
|
|
} else if (isolate_start_pfn < block_end_pfn) {
|
|
/*
|
|
* If isolation failed early, do not continue
|
|
* needlessly.
|
|
*/
|
|
break;
|
|
}
|
|
|
|
/* Adjust stride depending on isolation */
|
|
if (nr_isolated) {
|
|
stride = 1;
|
|
continue;
|
|
}
|
|
stride = min_t(unsigned int, COMPACT_CLUSTER_MAX, stride << 1);
|
|
}
|
|
|
|
/*
|
|
* Record where the free scanner will restart next time. Either we
|
|
* broke from the loop and set isolate_start_pfn based on the last
|
|
* call to isolate_freepages_block(), or we met the migration scanner
|
|
* and the loop terminated due to isolate_start_pfn < low_pfn
|
|
*/
|
|
cc->free_pfn = isolate_start_pfn;
|
|
|
|
splitmap:
|
|
/* __isolate_free_page() does not map the pages */
|
|
split_map_pages(freelist);
|
|
}
|
|
|
|
/*
|
|
* This is a migrate-callback that "allocates" freepages by taking pages
|
|
* from the isolated freelists in the block we are migrating to.
|
|
*/
|
|
static struct page *compaction_alloc(struct page *migratepage,
|
|
unsigned long data)
|
|
{
|
|
struct compact_control *cc = (struct compact_control *)data;
|
|
struct page *freepage;
|
|
|
|
if (list_empty(&cc->freepages)) {
|
|
isolate_freepages(cc);
|
|
|
|
if (list_empty(&cc->freepages))
|
|
return NULL;
|
|
}
|
|
|
|
freepage = list_entry(cc->freepages.next, struct page, lru);
|
|
list_del(&freepage->lru);
|
|
cc->nr_freepages--;
|
|
|
|
return freepage;
|
|
}
|
|
|
|
/*
|
|
* This is a migrate-callback that "frees" freepages back to the isolated
|
|
* freelist. All pages on the freelist are from the same zone, so there is no
|
|
* special handling needed for NUMA.
|
|
*/
|
|
static void compaction_free(struct page *page, unsigned long data)
|
|
{
|
|
struct compact_control *cc = (struct compact_control *)data;
|
|
|
|
list_add(&page->lru, &cc->freepages);
|
|
cc->nr_freepages++;
|
|
}
|
|
|
|
/* possible outcome of isolate_migratepages */
|
|
typedef enum {
|
|
ISOLATE_ABORT, /* Abort compaction now */
|
|
ISOLATE_NONE, /* No pages isolated, continue scanning */
|
|
ISOLATE_SUCCESS, /* Pages isolated, migrate */
|
|
} isolate_migrate_t;
|
|
|
|
/*
|
|
* Allow userspace to control policy on scanning the unevictable LRU for
|
|
* compactable pages.
|
|
*/
|
|
#ifdef CONFIG_PREEMPT_RT
|
|
int sysctl_compact_unevictable_allowed __read_mostly = 0;
|
|
#else
|
|
int sysctl_compact_unevictable_allowed __read_mostly = 1;
|
|
#endif
|
|
|
|
static inline void
|
|
update_fast_start_pfn(struct compact_control *cc, unsigned long pfn)
|
|
{
|
|
if (cc->fast_start_pfn == ULONG_MAX)
|
|
return;
|
|
|
|
if (!cc->fast_start_pfn)
|
|
cc->fast_start_pfn = pfn;
|
|
|
|
cc->fast_start_pfn = min(cc->fast_start_pfn, pfn);
|
|
}
|
|
|
|
static inline unsigned long
|
|
reinit_migrate_pfn(struct compact_control *cc)
|
|
{
|
|
if (!cc->fast_start_pfn || cc->fast_start_pfn == ULONG_MAX)
|
|
return cc->migrate_pfn;
|
|
|
|
cc->migrate_pfn = cc->fast_start_pfn;
|
|
cc->fast_start_pfn = ULONG_MAX;
|
|
|
|
return cc->migrate_pfn;
|
|
}
|
|
|
|
/*
|
|
* Briefly search the free lists for a migration source that already has
|
|
* some free pages to reduce the number of pages that need migration
|
|
* before a pageblock is free.
|
|
*/
|
|
static unsigned long fast_find_migrateblock(struct compact_control *cc)
|
|
{
|
|
unsigned int limit = freelist_scan_limit(cc);
|
|
unsigned int nr_scanned = 0;
|
|
unsigned long distance;
|
|
unsigned long pfn = cc->migrate_pfn;
|
|
unsigned long high_pfn;
|
|
int order;
|
|
bool found_block = false;
|
|
|
|
/* Skip hints are relied on to avoid repeats on the fast search */
|
|
if (cc->ignore_skip_hint)
|
|
return pfn;
|
|
|
|
/*
|
|
* If the migrate_pfn is not at the start of a zone or the start
|
|
* of a pageblock then assume this is a continuation of a previous
|
|
* scan restarted due to COMPACT_CLUSTER_MAX.
|
|
*/
|
|
if (pfn != cc->zone->zone_start_pfn && pfn != pageblock_start_pfn(pfn))
|
|
return pfn;
|
|
|
|
/*
|
|
* For smaller orders, just linearly scan as the number of pages
|
|
* to migrate should be relatively small and does not necessarily
|
|
* justify freeing up a large block for a small allocation.
|
|
*/
|
|
if (cc->order <= PAGE_ALLOC_COSTLY_ORDER)
|
|
return pfn;
|
|
|
|
/*
|
|
* Only allow kcompactd and direct requests for movable pages to
|
|
* quickly clear out a MOVABLE pageblock for allocation. This
|
|
* reduces the risk that a large movable pageblock is freed for
|
|
* an unmovable/reclaimable small allocation.
|
|
*/
|
|
if (cc->direct_compaction && cc->migratetype != MIGRATE_MOVABLE)
|
|
return pfn;
|
|
|
|
/*
|
|
* When starting the migration scanner, pick any pageblock within the
|
|
* first half of the search space. Otherwise try and pick a pageblock
|
|
* within the first eighth to reduce the chances that a migration
|
|
* target later becomes a source.
|
|
*/
|
|
distance = (cc->free_pfn - cc->migrate_pfn) >> 1;
|
|
if (cc->migrate_pfn != cc->zone->zone_start_pfn)
|
|
distance >>= 2;
|
|
high_pfn = pageblock_start_pfn(cc->migrate_pfn + distance);
|
|
|
|
for (order = cc->order - 1;
|
|
order >= PAGE_ALLOC_COSTLY_ORDER && !found_block && nr_scanned < limit;
|
|
order--) {
|
|
struct free_area *area = &cc->zone->free_area[order];
|
|
struct list_head *freelist;
|
|
unsigned long flags;
|
|
struct page *freepage;
|
|
|
|
if (!area->nr_free)
|
|
continue;
|
|
|
|
spin_lock_irqsave(&cc->zone->lock, flags);
|
|
freelist = &area->free_list[MIGRATE_MOVABLE];
|
|
list_for_each_entry(freepage, freelist, lru) {
|
|
unsigned long free_pfn;
|
|
|
|
if (nr_scanned++ >= limit) {
|
|
move_freelist_tail(freelist, freepage);
|
|
break;
|
|
}
|
|
|
|
free_pfn = page_to_pfn(freepage);
|
|
if (free_pfn < high_pfn) {
|
|
/*
|
|
* Avoid if skipped recently. Ideally it would
|
|
* move to the tail but even safe iteration of
|
|
* the list assumes an entry is deleted, not
|
|
* reordered.
|
|
*/
|
|
if (get_pageblock_skip(freepage))
|
|
continue;
|
|
|
|
/* Reorder to so a future search skips recent pages */
|
|
move_freelist_tail(freelist, freepage);
|
|
|
|
update_fast_start_pfn(cc, free_pfn);
|
|
pfn = pageblock_start_pfn(free_pfn);
|
|
cc->fast_search_fail = 0;
|
|
found_block = true;
|
|
set_pageblock_skip(freepage);
|
|
break;
|
|
}
|
|
}
|
|
spin_unlock_irqrestore(&cc->zone->lock, flags);
|
|
}
|
|
|
|
cc->total_migrate_scanned += nr_scanned;
|
|
|
|
/*
|
|
* If fast scanning failed then use a cached entry for a page block
|
|
* that had free pages as the basis for starting a linear scan.
|
|
*/
|
|
if (!found_block) {
|
|
cc->fast_search_fail++;
|
|
pfn = reinit_migrate_pfn(cc);
|
|
}
|
|
return pfn;
|
|
}
|
|
|
|
/*
|
|
* Isolate all pages that can be migrated from the first suitable block,
|
|
* starting at the block pointed to by the migrate scanner pfn within
|
|
* compact_control.
|
|
*/
|
|
static isolate_migrate_t isolate_migratepages(struct compact_control *cc)
|
|
{
|
|
unsigned long block_start_pfn;
|
|
unsigned long block_end_pfn;
|
|
unsigned long low_pfn;
|
|
struct page *page;
|
|
const isolate_mode_t isolate_mode =
|
|
(sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) |
|
|
(cc->mode != MIGRATE_SYNC ? ISOLATE_ASYNC_MIGRATE : 0);
|
|
bool fast_find_block;
|
|
|
|
/*
|
|
* Start at where we last stopped, or beginning of the zone as
|
|
* initialized by compact_zone(). The first failure will use
|
|
* the lowest PFN as the starting point for linear scanning.
|
|
*/
|
|
low_pfn = fast_find_migrateblock(cc);
|
|
block_start_pfn = pageblock_start_pfn(low_pfn);
|
|
if (block_start_pfn < cc->zone->zone_start_pfn)
|
|
block_start_pfn = cc->zone->zone_start_pfn;
|
|
|
|
/*
|
|
* fast_find_migrateblock marks a pageblock skipped so to avoid
|
|
* the isolation_suitable check below, check whether the fast
|
|
* search was successful.
|
|
*/
|
|
fast_find_block = low_pfn != cc->migrate_pfn && !cc->fast_search_fail;
|
|
|
|
/* Only scan within a pageblock boundary */
|
|
block_end_pfn = pageblock_end_pfn(low_pfn);
|
|
|
|
/*
|
|
* Iterate over whole pageblocks until we find the first suitable.
|
|
* Do not cross the free scanner.
|
|
*/
|
|
for (; block_end_pfn <= cc->free_pfn;
|
|
fast_find_block = false,
|
|
cc->migrate_pfn = low_pfn = block_end_pfn,
|
|
block_start_pfn = block_end_pfn,
|
|
block_end_pfn += pageblock_nr_pages) {
|
|
|
|
/*
|
|
* This can potentially iterate a massively long zone with
|
|
* many pageblocks unsuitable, so periodically check if we
|
|
* need to schedule.
|
|
*/
|
|
if (!(low_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages)))
|
|
cond_resched();
|
|
|
|
page = pageblock_pfn_to_page(block_start_pfn,
|
|
block_end_pfn, cc->zone);
|
|
if (!page)
|
|
continue;
|
|
|
|
/*
|
|
* If isolation recently failed, do not retry. Only check the
|
|
* pageblock once. COMPACT_CLUSTER_MAX causes a pageblock
|
|
* to be visited multiple times. Assume skip was checked
|
|
* before making it "skip" so other compaction instances do
|
|
* not scan the same block.
|
|
*/
|
|
if (IS_ALIGNED(low_pfn, pageblock_nr_pages) &&
|
|
!fast_find_block && !isolation_suitable(cc, page))
|
|
continue;
|
|
|
|
/*
|
|
* For async compaction, also only scan in MOVABLE blocks
|
|
* without huge pages. Async compaction is optimistic to see
|
|
* if the minimum amount of work satisfies the allocation.
|
|
* The cached PFN is updated as it's possible that all
|
|
* remaining blocks between source and target are unsuitable
|
|
* and the compaction scanners fail to meet.
|
|
*/
|
|
if (!suitable_migration_source(cc, page)) {
|
|
update_cached_migrate(cc, block_end_pfn);
|
|
continue;
|
|
}
|
|
|
|
/* Perform the isolation */
|
|
if (isolate_migratepages_block(cc, low_pfn, block_end_pfn,
|
|
isolate_mode))
|
|
return ISOLATE_ABORT;
|
|
|
|
/*
|
|
* Either we isolated something and proceed with migration. Or
|
|
* we failed and compact_zone should decide if we should
|
|
* continue or not.
|
|
*/
|
|
break;
|
|
}
|
|
|
|
return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE;
|
|
}
|
|
|
|
/*
|
|
* order == -1 is expected when compacting via
|
|
* /proc/sys/vm/compact_memory
|
|
*/
|
|
static inline bool is_via_compact_memory(int order)
|
|
{
|
|
return order == -1;
|
|
}
|
|
|
|
static bool kswapd_is_running(pg_data_t *pgdat)
|
|
{
|
|
return pgdat->kswapd && task_is_running(pgdat->kswapd);
|
|
}
|
|
|
|
/*
|
|
* A zone's fragmentation score is the external fragmentation wrt to the
|
|
* COMPACTION_HPAGE_ORDER. It returns a value in the range [0, 100].
|
|
*/
|
|
static unsigned int fragmentation_score_zone(struct zone *zone)
|
|
{
|
|
return extfrag_for_order(zone, COMPACTION_HPAGE_ORDER);
|
|
}
|
|
|
|
/*
|
|
* A weighted zone's fragmentation score is the external fragmentation
|
|
* wrt to the COMPACTION_HPAGE_ORDER scaled by the zone's size. It
|
|
* returns a value in the range [0, 100].
|
|
*
|
|
* The scaling factor ensures that proactive compaction focuses on larger
|
|
* zones like ZONE_NORMAL, rather than smaller, specialized zones like
|
|
* ZONE_DMA32. For smaller zones, the score value remains close to zero,
|
|
* and thus never exceeds the high threshold for proactive compaction.
|
|
*/
|
|
static unsigned int fragmentation_score_zone_weighted(struct zone *zone)
|
|
{
|
|
unsigned long score;
|
|
|
|
score = zone->present_pages * fragmentation_score_zone(zone);
|
|
return div64_ul(score, zone->zone_pgdat->node_present_pages + 1);
|
|
}
|
|
|
|
/*
|
|
* The per-node proactive (background) compaction process is started by its
|
|
* corresponding kcompactd thread when the node's fragmentation score
|
|
* exceeds the high threshold. The compaction process remains active till
|
|
* the node's score falls below the low threshold, or one of the back-off
|
|
* conditions is met.
|
|
*/
|
|
static unsigned int fragmentation_score_node(pg_data_t *pgdat)
|
|
{
|
|
unsigned int score = 0;
|
|
int zoneid;
|
|
|
|
for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
|
|
struct zone *zone;
|
|
|
|
zone = &pgdat->node_zones[zoneid];
|
|
score += fragmentation_score_zone_weighted(zone);
|
|
}
|
|
|
|
return score;
|
|
}
|
|
|
|
static unsigned int fragmentation_score_wmark(pg_data_t *pgdat, bool low)
|
|
{
|
|
unsigned int wmark_low;
|
|
|
|
/*
|
|
* Cap the low watermark to avoid excessive compaction
|
|
* activity in case a user sets the proactiveness tunable
|
|
* close to 100 (maximum).
|
|
*/
|
|
wmark_low = max(100U - sysctl_compaction_proactiveness, 5U);
|
|
return low ? wmark_low : min(wmark_low + 10, 100U);
|
|
}
|
|
|
|
static bool should_proactive_compact_node(pg_data_t *pgdat)
|
|
{
|
|
int wmark_high;
|
|
|
|
if (!sysctl_compaction_proactiveness || kswapd_is_running(pgdat))
|
|
return false;
|
|
|
|
wmark_high = fragmentation_score_wmark(pgdat, false);
|
|
return fragmentation_score_node(pgdat) > wmark_high;
|
|
}
|
|
|
|
static enum compact_result __compact_finished(struct compact_control *cc)
|
|
{
|
|
unsigned int order;
|
|
const int migratetype = cc->migratetype;
|
|
int ret;
|
|
|
|
/* Compaction run completes if the migrate and free scanner meet */
|
|
if (compact_scanners_met(cc)) {
|
|
/* Let the next compaction start anew. */
|
|
reset_cached_positions(cc->zone);
|
|
|
|
/*
|
|
* Mark that the PG_migrate_skip information should be cleared
|
|
* by kswapd when it goes to sleep. kcompactd does not set the
|
|
* flag itself as the decision to be clear should be directly
|
|
* based on an allocation request.
|
|
*/
|
|
if (cc->direct_compaction)
|
|
cc->zone->compact_blockskip_flush = true;
|
|
|
|
if (cc->whole_zone)
|
|
return COMPACT_COMPLETE;
|
|
else
|
|
return COMPACT_PARTIAL_SKIPPED;
|
|
}
|
|
|
|
if (cc->proactive_compaction) {
|
|
int score, wmark_low;
|
|
pg_data_t *pgdat;
|
|
|
|
pgdat = cc->zone->zone_pgdat;
|
|
if (kswapd_is_running(pgdat))
|
|
return COMPACT_PARTIAL_SKIPPED;
|
|
|
|
score = fragmentation_score_zone(cc->zone);
|
|
wmark_low = fragmentation_score_wmark(pgdat, true);
|
|
|
|
if (score > wmark_low)
|
|
ret = COMPACT_CONTINUE;
|
|
else
|
|
ret = COMPACT_SUCCESS;
|
|
|
|
goto out;
|
|
}
|
|
|
|
if (is_via_compact_memory(cc->order))
|
|
return COMPACT_CONTINUE;
|
|
|
|
/*
|
|
* Always finish scanning a pageblock to reduce the possibility of
|
|
* fallbacks in the future. This is particularly important when
|
|
* migration source is unmovable/reclaimable but it's not worth
|
|
* special casing.
|
|
*/
|
|
if (!IS_ALIGNED(cc->migrate_pfn, pageblock_nr_pages))
|
|
return COMPACT_CONTINUE;
|
|
|
|
/* Direct compactor: Is a suitable page free? */
|
|
ret = COMPACT_NO_SUITABLE_PAGE;
|
|
for (order = cc->order; order < MAX_ORDER; order++) {
|
|
struct free_area *area = &cc->zone->free_area[order];
|
|
bool can_steal;
|
|
|
|
/* Job done if page is free of the right migratetype */
|
|
if (!free_area_empty(area, migratetype))
|
|
return COMPACT_SUCCESS;
|
|
|
|
#ifdef CONFIG_CMA
|
|
/* MIGRATE_MOVABLE can fallback on MIGRATE_CMA */
|
|
if (migratetype == MIGRATE_MOVABLE &&
|
|
!free_area_empty(area, MIGRATE_CMA))
|
|
return COMPACT_SUCCESS;
|
|
#endif
|
|
/*
|
|
* Job done if allocation would steal freepages from
|
|
* other migratetype buddy lists.
|
|
*/
|
|
if (find_suitable_fallback(area, order, migratetype,
|
|
true, &can_steal) != -1) {
|
|
|
|
/* movable pages are OK in any pageblock */
|
|
if (migratetype == MIGRATE_MOVABLE)
|
|
return COMPACT_SUCCESS;
|
|
|
|
/*
|
|
* We are stealing for a non-movable allocation. Make
|
|
* sure we finish compacting the current pageblock
|
|
* first so it is as free as possible and we won't
|
|
* have to steal another one soon. This only applies
|
|
* to sync compaction, as async compaction operates
|
|
* on pageblocks of the same migratetype.
|
|
*/
|
|
if (cc->mode == MIGRATE_ASYNC ||
|
|
IS_ALIGNED(cc->migrate_pfn,
|
|
pageblock_nr_pages)) {
|
|
return COMPACT_SUCCESS;
|
|
}
|
|
|
|
ret = COMPACT_CONTINUE;
|
|
break;
|
|
}
|
|
}
|
|
|
|
out:
|
|
if (cc->contended || fatal_signal_pending(current))
|
|
ret = COMPACT_CONTENDED;
|
|
|
|
return ret;
|
|
}
|
|
|
|
static enum compact_result compact_finished(struct compact_control *cc)
|
|
{
|
|
int ret;
|
|
|
|
ret = __compact_finished(cc);
|
|
trace_mm_compaction_finished(cc->zone, cc->order, ret);
|
|
if (ret == COMPACT_NO_SUITABLE_PAGE)
|
|
ret = COMPACT_CONTINUE;
|
|
|
|
return ret;
|
|
}
|
|
|
|
static enum compact_result __compaction_suitable(struct zone *zone, int order,
|
|
unsigned int alloc_flags,
|
|
int highest_zoneidx,
|
|
unsigned long wmark_target)
|
|
{
|
|
unsigned long watermark;
|
|
|
|
if (is_via_compact_memory(order))
|
|
return COMPACT_CONTINUE;
|
|
|
|
watermark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK);
|
|
/*
|
|
* If watermarks for high-order allocation are already met, there
|
|
* should be no need for compaction at all.
|
|
*/
|
|
if (zone_watermark_ok(zone, order, watermark, highest_zoneidx,
|
|
alloc_flags))
|
|
return COMPACT_SUCCESS;
|
|
|
|
/*
|
|
* Watermarks for order-0 must be met for compaction to be able to
|
|
* isolate free pages for migration targets. This means that the
|
|
* watermark and alloc_flags have to match, or be more pessimistic than
|
|
* the check in __isolate_free_page(). We don't use the direct
|
|
* compactor's alloc_flags, as they are not relevant for freepage
|
|
* isolation. We however do use the direct compactor's highest_zoneidx
|
|
* to skip over zones where lowmem reserves would prevent allocation
|
|
* even if compaction succeeds.
|
|
* For costly orders, we require low watermark instead of min for
|
|
* compaction to proceed to increase its chances.
|
|
* ALLOC_CMA is used, as pages in CMA pageblocks are considered
|
|
* suitable migration targets
|
|
*/
|
|
watermark = (order > PAGE_ALLOC_COSTLY_ORDER) ?
|
|
low_wmark_pages(zone) : min_wmark_pages(zone);
|
|
watermark += compact_gap(order);
|
|
if (!__zone_watermark_ok(zone, 0, watermark, highest_zoneidx,
|
|
ALLOC_CMA, wmark_target))
|
|
return COMPACT_SKIPPED;
|
|
|
|
return COMPACT_CONTINUE;
|
|
}
|
|
|
|
/*
|
|
* compaction_suitable: Is this suitable to run compaction on this zone now?
|
|
* Returns
|
|
* COMPACT_SKIPPED - If there are too few free pages for compaction
|
|
* COMPACT_SUCCESS - If the allocation would succeed without compaction
|
|
* COMPACT_CONTINUE - If compaction should run now
|
|
*/
|
|
enum compact_result compaction_suitable(struct zone *zone, int order,
|
|
unsigned int alloc_flags,
|
|
int highest_zoneidx)
|
|
{
|
|
enum compact_result ret;
|
|
int fragindex;
|
|
|
|
ret = __compaction_suitable(zone, order, alloc_flags, highest_zoneidx,
|
|
zone_page_state(zone, NR_FREE_PAGES));
|
|
/*
|
|
* fragmentation index determines if allocation failures are due to
|
|
* low memory or external fragmentation
|
|
*
|
|
* index of -1000 would imply allocations might succeed depending on
|
|
* watermarks, but we already failed the high-order watermark check
|
|
* index towards 0 implies failure is due to lack of memory
|
|
* index towards 1000 implies failure is due to fragmentation
|
|
*
|
|
* Only compact if a failure would be due to fragmentation. Also
|
|
* ignore fragindex for non-costly orders where the alternative to
|
|
* a successful reclaim/compaction is OOM. Fragindex and the
|
|
* vm.extfrag_threshold sysctl is meant as a heuristic to prevent
|
|
* excessive compaction for costly orders, but it should not be at the
|
|
* expense of system stability.
|
|
*/
|
|
if (ret == COMPACT_CONTINUE && (order > PAGE_ALLOC_COSTLY_ORDER)) {
|
|
fragindex = fragmentation_index(zone, order);
|
|
if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
|
|
ret = COMPACT_NOT_SUITABLE_ZONE;
|
|
}
|
|
|
|
trace_mm_compaction_suitable(zone, order, ret);
|
|
if (ret == COMPACT_NOT_SUITABLE_ZONE)
|
|
ret = COMPACT_SKIPPED;
|
|
|
|
return ret;
|
|
}
|
|
|
|
bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
|
|
int alloc_flags)
|
|
{
|
|
struct zone *zone;
|
|
struct zoneref *z;
|
|
|
|
/*
|
|
* Make sure at least one zone would pass __compaction_suitable if we continue
|
|
* retrying the reclaim.
|
|
*/
|
|
for_each_zone_zonelist_nodemask(zone, z, ac->zonelist,
|
|
ac->highest_zoneidx, ac->nodemask) {
|
|
unsigned long available;
|
|
enum compact_result compact_result;
|
|
|
|
/*
|
|
* Do not consider all the reclaimable memory because we do not
|
|
* want to trash just for a single high order allocation which
|
|
* is even not guaranteed to appear even if __compaction_suitable
|
|
* is happy about the watermark check.
|
|
*/
|
|
available = zone_reclaimable_pages(zone) / order;
|
|
available += zone_page_state_snapshot(zone, NR_FREE_PAGES);
|
|
compact_result = __compaction_suitable(zone, order, alloc_flags,
|
|
ac->highest_zoneidx, available);
|
|
if (compact_result != COMPACT_SKIPPED)
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
static enum compact_result
|
|
compact_zone(struct compact_control *cc, struct capture_control *capc)
|
|
{
|
|
enum compact_result ret;
|
|
unsigned long start_pfn = cc->zone->zone_start_pfn;
|
|
unsigned long end_pfn = zone_end_pfn(cc->zone);
|
|
unsigned long last_migrated_pfn;
|
|
const bool sync = cc->mode != MIGRATE_ASYNC;
|
|
bool update_cached;
|
|
unsigned int nr_succeeded = 0;
|
|
|
|
/*
|
|
* These counters track activities during zone compaction. Initialize
|
|
* them before compacting a new zone.
|
|
*/
|
|
cc->total_migrate_scanned = 0;
|
|
cc->total_free_scanned = 0;
|
|
cc->nr_migratepages = 0;
|
|
cc->nr_freepages = 0;
|
|
INIT_LIST_HEAD(&cc->freepages);
|
|
INIT_LIST_HEAD(&cc->migratepages);
|
|
|
|
cc->migratetype = gfp_migratetype(cc->gfp_mask);
|
|
ret = compaction_suitable(cc->zone, cc->order, cc->alloc_flags,
|
|
cc->highest_zoneidx);
|
|
/* Compaction is likely to fail */
|
|
if (ret == COMPACT_SUCCESS || ret == COMPACT_SKIPPED)
|
|
return ret;
|
|
|
|
/* huh, compaction_suitable is returning something unexpected */
|
|
VM_BUG_ON(ret != COMPACT_CONTINUE);
|
|
|
|
/*
|
|
* Clear pageblock skip if there were failures recently and compaction
|
|
* is about to be retried after being deferred.
|
|
*/
|
|
if (compaction_restarting(cc->zone, cc->order))
|
|
__reset_isolation_suitable(cc->zone);
|
|
|
|
/*
|
|
* Setup to move all movable pages to the end of the zone. Used cached
|
|
* information on where the scanners should start (unless we explicitly
|
|
* want to compact the whole zone), but check that it is initialised
|
|
* by ensuring the values are within zone boundaries.
|
|
*/
|
|
cc->fast_start_pfn = 0;
|
|
if (cc->whole_zone) {
|
|
cc->migrate_pfn = start_pfn;
|
|
cc->free_pfn = pageblock_start_pfn(end_pfn - 1);
|
|
} else {
|
|
cc->migrate_pfn = cc->zone->compact_cached_migrate_pfn[sync];
|
|
cc->free_pfn = cc->zone->compact_cached_free_pfn;
|
|
if (cc->free_pfn < start_pfn || cc->free_pfn >= end_pfn) {
|
|
cc->free_pfn = pageblock_start_pfn(end_pfn - 1);
|
|
cc->zone->compact_cached_free_pfn = cc->free_pfn;
|
|
}
|
|
if (cc->migrate_pfn < start_pfn || cc->migrate_pfn >= end_pfn) {
|
|
cc->migrate_pfn = start_pfn;
|
|
cc->zone->compact_cached_migrate_pfn[0] = cc->migrate_pfn;
|
|
cc->zone->compact_cached_migrate_pfn[1] = cc->migrate_pfn;
|
|
}
|
|
|
|
if (cc->migrate_pfn <= cc->zone->compact_init_migrate_pfn)
|
|
cc->whole_zone = true;
|
|
}
|
|
|
|
last_migrated_pfn = 0;
|
|
|
|
/*
|
|
* Migrate has separate cached PFNs for ASYNC and SYNC* migration on
|
|
* the basis that some migrations will fail in ASYNC mode. However,
|
|
* if the cached PFNs match and pageblocks are skipped due to having
|
|
* no isolation candidates, then the sync state does not matter.
|
|
* Until a pageblock with isolation candidates is found, keep the
|
|
* cached PFNs in sync to avoid revisiting the same blocks.
|
|
*/
|
|
update_cached = !sync &&
|
|
cc->zone->compact_cached_migrate_pfn[0] == cc->zone->compact_cached_migrate_pfn[1];
|
|
|
|
trace_mm_compaction_begin(cc, start_pfn, end_pfn, sync);
|
|
|
|
/* lru_add_drain_all could be expensive with involving other CPUs */
|
|
lru_add_drain();
|
|
|
|
while ((ret = compact_finished(cc)) == COMPACT_CONTINUE) {
|
|
int err;
|
|
unsigned long iteration_start_pfn = cc->migrate_pfn;
|
|
|
|
/*
|
|
* Avoid multiple rescans which can happen if a page cannot be
|
|
* isolated (dirty/writeback in async mode) or if the migrated
|
|
* pages are being allocated before the pageblock is cleared.
|
|
* The first rescan will capture the entire pageblock for
|
|
* migration. If it fails, it'll be marked skip and scanning
|
|
* will proceed as normal.
|
|
*/
|
|
cc->rescan = false;
|
|
if (pageblock_start_pfn(last_migrated_pfn) ==
|
|
pageblock_start_pfn(iteration_start_pfn)) {
|
|
cc->rescan = true;
|
|
}
|
|
|
|
switch (isolate_migratepages(cc)) {
|
|
case ISOLATE_ABORT:
|
|
ret = COMPACT_CONTENDED;
|
|
putback_movable_pages(&cc->migratepages);
|
|
cc->nr_migratepages = 0;
|
|
goto out;
|
|
case ISOLATE_NONE:
|
|
if (update_cached) {
|
|
cc->zone->compact_cached_migrate_pfn[1] =
|
|
cc->zone->compact_cached_migrate_pfn[0];
|
|
}
|
|
|
|
/*
|
|
* We haven't isolated and migrated anything, but
|
|
* there might still be unflushed migrations from
|
|
* previous cc->order aligned block.
|
|
*/
|
|
goto check_drain;
|
|
case ISOLATE_SUCCESS:
|
|
update_cached = false;
|
|
last_migrated_pfn = iteration_start_pfn;
|
|
}
|
|
|
|
err = migrate_pages(&cc->migratepages, compaction_alloc,
|
|
compaction_free, (unsigned long)cc, cc->mode,
|
|
MR_COMPACTION, &nr_succeeded);
|
|
|
|
trace_mm_compaction_migratepages(cc, nr_succeeded);
|
|
|
|
/* All pages were either migrated or will be released */
|
|
cc->nr_migratepages = 0;
|
|
if (err) {
|
|
putback_movable_pages(&cc->migratepages);
|
|
/*
|
|
* migrate_pages() may return -ENOMEM when scanners meet
|
|
* and we want compact_finished() to detect it
|
|
*/
|
|
if (err == -ENOMEM && !compact_scanners_met(cc)) {
|
|
ret = COMPACT_CONTENDED;
|
|
goto out;
|
|
}
|
|
/*
|
|
* We failed to migrate at least one page in the current
|
|
* order-aligned block, so skip the rest of it.
|
|
*/
|
|
if (cc->direct_compaction &&
|
|
(cc->mode == MIGRATE_ASYNC)) {
|
|
cc->migrate_pfn = block_end_pfn(
|
|
cc->migrate_pfn - 1, cc->order);
|
|
/* Draining pcplists is useless in this case */
|
|
last_migrated_pfn = 0;
|
|
}
|
|
}
|
|
|
|
check_drain:
|
|
/*
|
|
* Has the migration scanner moved away from the previous
|
|
* cc->order aligned block where we migrated from? If yes,
|
|
* flush the pages that were freed, so that they can merge and
|
|
* compact_finished() can detect immediately if allocation
|
|
* would succeed.
|
|
*/
|
|
if (cc->order > 0 && last_migrated_pfn) {
|
|
unsigned long current_block_start =
|
|
block_start_pfn(cc->migrate_pfn, cc->order);
|
|
|
|
if (last_migrated_pfn < current_block_start) {
|
|
lru_add_drain_cpu_zone(cc->zone);
|
|
/* No more flushing until we migrate again */
|
|
last_migrated_pfn = 0;
|
|
}
|
|
}
|
|
|
|
/* Stop if a page has been captured */
|
|
if (capc && capc->page) {
|
|
ret = COMPACT_SUCCESS;
|
|
break;
|
|
}
|
|
}
|
|
|
|
out:
|
|
/*
|
|
* Release free pages and update where the free scanner should restart,
|
|
* so we don't leave any returned pages behind in the next attempt.
|
|
*/
|
|
if (cc->nr_freepages > 0) {
|
|
unsigned long free_pfn = release_freepages(&cc->freepages);
|
|
|
|
cc->nr_freepages = 0;
|
|
VM_BUG_ON(free_pfn == 0);
|
|
/* The cached pfn is always the first in a pageblock */
|
|
free_pfn = pageblock_start_pfn(free_pfn);
|
|
/*
|
|
* Only go back, not forward. The cached pfn might have been
|
|
* already reset to zone end in compact_finished()
|
|
*/
|
|
if (free_pfn > cc->zone->compact_cached_free_pfn)
|
|
cc->zone->compact_cached_free_pfn = free_pfn;
|
|
}
|
|
|
|
count_compact_events(COMPACTMIGRATE_SCANNED, cc->total_migrate_scanned);
|
|
count_compact_events(COMPACTFREE_SCANNED, cc->total_free_scanned);
|
|
|
|
trace_mm_compaction_end(cc, start_pfn, end_pfn, sync, ret);
|
|
|
|
return ret;
|
|
}
|
|
|
|
static enum compact_result compact_zone_order(struct zone *zone, int order,
|
|
gfp_t gfp_mask, enum compact_priority prio,
|
|
unsigned int alloc_flags, int highest_zoneidx,
|
|
struct page **capture)
|
|
{
|
|
enum compact_result ret;
|
|
struct compact_control cc = {
|
|
.order = order,
|
|
.search_order = order,
|
|
.gfp_mask = gfp_mask,
|
|
.zone = zone,
|
|
.mode = (prio == COMPACT_PRIO_ASYNC) ?
|
|
MIGRATE_ASYNC : MIGRATE_SYNC_LIGHT,
|
|
.alloc_flags = alloc_flags,
|
|
.highest_zoneidx = highest_zoneidx,
|
|
.direct_compaction = true,
|
|
.whole_zone = (prio == MIN_COMPACT_PRIORITY),
|
|
.ignore_skip_hint = (prio == MIN_COMPACT_PRIORITY),
|
|
.ignore_block_suitable = (prio == MIN_COMPACT_PRIORITY)
|
|
};
|
|
struct capture_control capc = {
|
|
.cc = &cc,
|
|
.page = NULL,
|
|
};
|
|
|
|
/*
|
|
* Make sure the structs are really initialized before we expose the
|
|
* capture control, in case we are interrupted and the interrupt handler
|
|
* frees a page.
|
|
*/
|
|
barrier();
|
|
WRITE_ONCE(current->capture_control, &capc);
|
|
|
|
ret = compact_zone(&cc, &capc);
|
|
|
|
VM_BUG_ON(!list_empty(&cc.freepages));
|
|
VM_BUG_ON(!list_empty(&cc.migratepages));
|
|
|
|
/*
|
|
* Make sure we hide capture control first before we read the captured
|
|
* page pointer, otherwise an interrupt could free and capture a page
|
|
* and we would leak it.
|
|
*/
|
|
WRITE_ONCE(current->capture_control, NULL);
|
|
*capture = READ_ONCE(capc.page);
|
|
/*
|
|
* Technically, it is also possible that compaction is skipped but
|
|
* the page is still captured out of luck(IRQ came and freed the page).
|
|
* Returning COMPACT_SUCCESS in such cases helps in properly accounting
|
|
* the COMPACT[STALL|FAIL] when compaction is skipped.
|
|
*/
|
|
if (*capture)
|
|
ret = COMPACT_SUCCESS;
|
|
|
|
return ret;
|
|
}
|
|
|
|
int sysctl_extfrag_threshold = 500;
|
|
|
|
/**
|
|
* try_to_compact_pages - Direct compact to satisfy a high-order allocation
|
|
* @gfp_mask: The GFP mask of the current allocation
|
|
* @order: The order of the current allocation
|
|
* @alloc_flags: The allocation flags of the current allocation
|
|
* @ac: The context of current allocation
|
|
* @prio: Determines how hard direct compaction should try to succeed
|
|
* @capture: Pointer to free page created by compaction will be stored here
|
|
*
|
|
* This is the main entry point for direct page compaction.
|
|
*/
|
|
enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order,
|
|
unsigned int alloc_flags, const struct alloc_context *ac,
|
|
enum compact_priority prio, struct page **capture)
|
|
{
|
|
int may_perform_io = gfp_mask & __GFP_IO;
|
|
struct zoneref *z;
|
|
struct zone *zone;
|
|
enum compact_result rc = COMPACT_SKIPPED;
|
|
|
|
/*
|
|
* Check if the GFP flags allow compaction - GFP_NOIO is really
|
|
* tricky context because the migration might require IO
|
|
*/
|
|
if (!may_perform_io)
|
|
return COMPACT_SKIPPED;
|
|
|
|
trace_mm_compaction_try_to_compact_pages(order, gfp_mask, prio);
|
|
|
|
/* Compact each zone in the list */
|
|
for_each_zone_zonelist_nodemask(zone, z, ac->zonelist,
|
|
ac->highest_zoneidx, ac->nodemask) {
|
|
enum compact_result status;
|
|
|
|
if (prio > MIN_COMPACT_PRIORITY
|
|
&& compaction_deferred(zone, order)) {
|
|
rc = max_t(enum compact_result, COMPACT_DEFERRED, rc);
|
|
continue;
|
|
}
|
|
|
|
status = compact_zone_order(zone, order, gfp_mask, prio,
|
|
alloc_flags, ac->highest_zoneidx, capture);
|
|
rc = max(status, rc);
|
|
|
|
/* The allocation should succeed, stop compacting */
|
|
if (status == COMPACT_SUCCESS) {
|
|
/*
|
|
* We think the allocation will succeed in this zone,
|
|
* but it is not certain, hence the false. The caller
|
|
* will repeat this with true if allocation indeed
|
|
* succeeds in this zone.
|
|
*/
|
|
compaction_defer_reset(zone, order, false);
|
|
|
|
break;
|
|
}
|
|
|
|
if (prio != COMPACT_PRIO_ASYNC && (status == COMPACT_COMPLETE ||
|
|
status == COMPACT_PARTIAL_SKIPPED))
|
|
/*
|
|
* We think that allocation won't succeed in this zone
|
|
* so we defer compaction there. If it ends up
|
|
* succeeding after all, it will be reset.
|
|
*/
|
|
defer_compaction(zone, order);
|
|
|
|
/*
|
|
* We might have stopped compacting due to need_resched() in
|
|
* async compaction, or due to a fatal signal detected. In that
|
|
* case do not try further zones
|
|
*/
|
|
if ((prio == COMPACT_PRIO_ASYNC && need_resched())
|
|
|| fatal_signal_pending(current))
|
|
break;
|
|
}
|
|
|
|
return rc;
|
|
}
|
|
|
|
/*
|
|
* Compact all zones within a node till each zone's fragmentation score
|
|
* reaches within proactive compaction thresholds (as determined by the
|
|
* proactiveness tunable).
|
|
*
|
|
* It is possible that the function returns before reaching score targets
|
|
* due to various back-off conditions, such as, contention on per-node or
|
|
* per-zone locks.
|
|
*/
|
|
static void proactive_compact_node(pg_data_t *pgdat)
|
|
{
|
|
int zoneid;
|
|
struct zone *zone;
|
|
struct compact_control cc = {
|
|
.order = -1,
|
|
.mode = MIGRATE_SYNC_LIGHT,
|
|
.ignore_skip_hint = true,
|
|
.whole_zone = true,
|
|
.gfp_mask = GFP_KERNEL,
|
|
.proactive_compaction = true,
|
|
};
|
|
|
|
for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
|
|
zone = &pgdat->node_zones[zoneid];
|
|
if (!populated_zone(zone))
|
|
continue;
|
|
|
|
cc.zone = zone;
|
|
|
|
compact_zone(&cc, NULL);
|
|
|
|
VM_BUG_ON(!list_empty(&cc.freepages));
|
|
VM_BUG_ON(!list_empty(&cc.migratepages));
|
|
}
|
|
}
|
|
|
|
/* Compact all zones within a node */
|
|
static void compact_node(int nid)
|
|
{
|
|
pg_data_t *pgdat = NODE_DATA(nid);
|
|
int zoneid;
|
|
struct zone *zone;
|
|
struct compact_control cc = {
|
|
.order = -1,
|
|
.mode = MIGRATE_SYNC,
|
|
.ignore_skip_hint = true,
|
|
.whole_zone = true,
|
|
.gfp_mask = GFP_KERNEL,
|
|
};
|
|
|
|
|
|
for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
|
|
|
|
zone = &pgdat->node_zones[zoneid];
|
|
if (!populated_zone(zone))
|
|
continue;
|
|
|
|
cc.zone = zone;
|
|
|
|
compact_zone(&cc, NULL);
|
|
|
|
VM_BUG_ON(!list_empty(&cc.freepages));
|
|
VM_BUG_ON(!list_empty(&cc.migratepages));
|
|
}
|
|
}
|
|
|
|
/* Compact all nodes in the system */
|
|
static void compact_nodes(void)
|
|
{
|
|
int nid;
|
|
|
|
/* Flush pending updates to the LRU lists */
|
|
lru_add_drain_all();
|
|
|
|
for_each_online_node(nid)
|
|
compact_node(nid);
|
|
}
|
|
|
|
/*
|
|
* Tunable for proactive compaction. It determines how
|
|
* aggressively the kernel should compact memory in the
|
|
* background. It takes values in the range [0, 100].
|
|
*/
|
|
unsigned int __read_mostly sysctl_compaction_proactiveness = 20;
|
|
|
|
int compaction_proactiveness_sysctl_handler(struct ctl_table *table, int write,
|
|
void *buffer, size_t *length, loff_t *ppos)
|
|
{
|
|
int rc, nid;
|
|
|
|
rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
|
|
if (rc)
|
|
return rc;
|
|
|
|
if (write && sysctl_compaction_proactiveness) {
|
|
for_each_online_node(nid) {
|
|
pg_data_t *pgdat = NODE_DATA(nid);
|
|
|
|
if (pgdat->proactive_compact_trigger)
|
|
continue;
|
|
|
|
pgdat->proactive_compact_trigger = true;
|
|
wake_up_interruptible(&pgdat->kcompactd_wait);
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* This is the entry point for compacting all nodes via
|
|
* /proc/sys/vm/compact_memory
|
|
*/
|
|
int sysctl_compaction_handler(struct ctl_table *table, int write,
|
|
void *buffer, size_t *length, loff_t *ppos)
|
|
{
|
|
if (write)
|
|
compact_nodes();
|
|
|
|
return 0;
|
|
}
|
|
|
|
#if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
|
|
static ssize_t compact_store(struct device *dev,
|
|
struct device_attribute *attr,
|
|
const char *buf, size_t count)
|
|
{
|
|
int nid = dev->id;
|
|
|
|
if (nid >= 0 && nid < nr_node_ids && node_online(nid)) {
|
|
/* Flush pending updates to the LRU lists */
|
|
lru_add_drain_all();
|
|
|
|
compact_node(nid);
|
|
}
|
|
|
|
return count;
|
|
}
|
|
static DEVICE_ATTR_WO(compact);
|
|
|
|
int compaction_register_node(struct node *node)
|
|
{
|
|
return device_create_file(&node->dev, &dev_attr_compact);
|
|
}
|
|
|
|
void compaction_unregister_node(struct node *node)
|
|
{
|
|
return device_remove_file(&node->dev, &dev_attr_compact);
|
|
}
|
|
#endif /* CONFIG_SYSFS && CONFIG_NUMA */
|
|
|
|
static inline bool kcompactd_work_requested(pg_data_t *pgdat)
|
|
{
|
|
return pgdat->kcompactd_max_order > 0 || kthread_should_stop() ||
|
|
pgdat->proactive_compact_trigger;
|
|
}
|
|
|
|
static bool kcompactd_node_suitable(pg_data_t *pgdat)
|
|
{
|
|
int zoneid;
|
|
struct zone *zone;
|
|
enum zone_type highest_zoneidx = pgdat->kcompactd_highest_zoneidx;
|
|
|
|
for (zoneid = 0; zoneid <= highest_zoneidx; zoneid++) {
|
|
zone = &pgdat->node_zones[zoneid];
|
|
|
|
if (!populated_zone(zone))
|
|
continue;
|
|
|
|
if (compaction_suitable(zone, pgdat->kcompactd_max_order, 0,
|
|
highest_zoneidx) == COMPACT_CONTINUE)
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
static void kcompactd_do_work(pg_data_t *pgdat)
|
|
{
|
|
/*
|
|
* With no special task, compact all zones so that a page of requested
|
|
* order is allocatable.
|
|
*/
|
|
int zoneid;
|
|
struct zone *zone;
|
|
struct compact_control cc = {
|
|
.order = pgdat->kcompactd_max_order,
|
|
.search_order = pgdat->kcompactd_max_order,
|
|
.highest_zoneidx = pgdat->kcompactd_highest_zoneidx,
|
|
.mode = MIGRATE_SYNC_LIGHT,
|
|
.ignore_skip_hint = false,
|
|
.gfp_mask = GFP_KERNEL,
|
|
};
|
|
trace_mm_compaction_kcompactd_wake(pgdat->node_id, cc.order,
|
|
cc.highest_zoneidx);
|
|
count_compact_event(KCOMPACTD_WAKE);
|
|
|
|
for (zoneid = 0; zoneid <= cc.highest_zoneidx; zoneid++) {
|
|
int status;
|
|
|
|
zone = &pgdat->node_zones[zoneid];
|
|
if (!populated_zone(zone))
|
|
continue;
|
|
|
|
if (compaction_deferred(zone, cc.order))
|
|
continue;
|
|
|
|
if (compaction_suitable(zone, cc.order, 0, zoneid) !=
|
|
COMPACT_CONTINUE)
|
|
continue;
|
|
|
|
if (kthread_should_stop())
|
|
return;
|
|
|
|
cc.zone = zone;
|
|
status = compact_zone(&cc, NULL);
|
|
|
|
if (status == COMPACT_SUCCESS) {
|
|
compaction_defer_reset(zone, cc.order, false);
|
|
} else if (status == COMPACT_PARTIAL_SKIPPED || status == COMPACT_COMPLETE) {
|
|
/*
|
|
* Buddy pages may become stranded on pcps that could
|
|
* otherwise coalesce on the zone's free area for
|
|
* order >= cc.order. This is ratelimited by the
|
|
* upcoming deferral.
|
|
*/
|
|
drain_all_pages(zone);
|
|
|
|
/*
|
|
* We use sync migration mode here, so we defer like
|
|
* sync direct compaction does.
|
|
*/
|
|
defer_compaction(zone, cc.order);
|
|
}
|
|
|
|
count_compact_events(KCOMPACTD_MIGRATE_SCANNED,
|
|
cc.total_migrate_scanned);
|
|
count_compact_events(KCOMPACTD_FREE_SCANNED,
|
|
cc.total_free_scanned);
|
|
|
|
VM_BUG_ON(!list_empty(&cc.freepages));
|
|
VM_BUG_ON(!list_empty(&cc.migratepages));
|
|
}
|
|
|
|
/*
|
|
* Regardless of success, we are done until woken up next. But remember
|
|
* the requested order/highest_zoneidx in case it was higher/tighter
|
|
* than our current ones
|
|
*/
|
|
if (pgdat->kcompactd_max_order <= cc.order)
|
|
pgdat->kcompactd_max_order = 0;
|
|
if (pgdat->kcompactd_highest_zoneidx >= cc.highest_zoneidx)
|
|
pgdat->kcompactd_highest_zoneidx = pgdat->nr_zones - 1;
|
|
}
|
|
|
|
void wakeup_kcompactd(pg_data_t *pgdat, int order, int highest_zoneidx)
|
|
{
|
|
if (!order)
|
|
return;
|
|
|
|
if (pgdat->kcompactd_max_order < order)
|
|
pgdat->kcompactd_max_order = order;
|
|
|
|
if (pgdat->kcompactd_highest_zoneidx > highest_zoneidx)
|
|
pgdat->kcompactd_highest_zoneidx = highest_zoneidx;
|
|
|
|
/*
|
|
* Pairs with implicit barrier in wait_event_freezable()
|
|
* such that wakeups are not missed.
|
|
*/
|
|
if (!wq_has_sleeper(&pgdat->kcompactd_wait))
|
|
return;
|
|
|
|
if (!kcompactd_node_suitable(pgdat))
|
|
return;
|
|
|
|
trace_mm_compaction_wakeup_kcompactd(pgdat->node_id, order,
|
|
highest_zoneidx);
|
|
wake_up_interruptible(&pgdat->kcompactd_wait);
|
|
}
|
|
|
|
/*
|
|
* The background compaction daemon, started as a kernel thread
|
|
* from the init process.
|
|
*/
|
|
static int kcompactd(void *p)
|
|
{
|
|
pg_data_t *pgdat = (pg_data_t *)p;
|
|
struct task_struct *tsk = current;
|
|
long default_timeout = msecs_to_jiffies(HPAGE_FRAG_CHECK_INTERVAL_MSEC);
|
|
long timeout = default_timeout;
|
|
|
|
const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
|
|
|
|
if (!cpumask_empty(cpumask))
|
|
set_cpus_allowed_ptr(tsk, cpumask);
|
|
|
|
set_freezable();
|
|
|
|
pgdat->kcompactd_max_order = 0;
|
|
pgdat->kcompactd_highest_zoneidx = pgdat->nr_zones - 1;
|
|
|
|
while (!kthread_should_stop()) {
|
|
unsigned long pflags;
|
|
|
|
/*
|
|
* Avoid the unnecessary wakeup for proactive compaction
|
|
* when it is disabled.
|
|
*/
|
|
if (!sysctl_compaction_proactiveness)
|
|
timeout = MAX_SCHEDULE_TIMEOUT;
|
|
trace_mm_compaction_kcompactd_sleep(pgdat->node_id);
|
|
if (wait_event_freezable_timeout(pgdat->kcompactd_wait,
|
|
kcompactd_work_requested(pgdat), timeout) &&
|
|
!pgdat->proactive_compact_trigger) {
|
|
|
|
psi_memstall_enter(&pflags);
|
|
kcompactd_do_work(pgdat);
|
|
psi_memstall_leave(&pflags);
|
|
/*
|
|
* Reset the timeout value. The defer timeout from
|
|
* proactive compaction is lost here but that is fine
|
|
* as the condition of the zone changing substantionally
|
|
* then carrying on with the previous defer interval is
|
|
* not useful.
|
|
*/
|
|
timeout = default_timeout;
|
|
continue;
|
|
}
|
|
|
|
/*
|
|
* Start the proactive work with default timeout. Based
|
|
* on the fragmentation score, this timeout is updated.
|
|
*/
|
|
timeout = default_timeout;
|
|
if (should_proactive_compact_node(pgdat)) {
|
|
unsigned int prev_score, score;
|
|
|
|
prev_score = fragmentation_score_node(pgdat);
|
|
proactive_compact_node(pgdat);
|
|
score = fragmentation_score_node(pgdat);
|
|
/*
|
|
* Defer proactive compaction if the fragmentation
|
|
* score did not go down i.e. no progress made.
|
|
*/
|
|
if (unlikely(score >= prev_score))
|
|
timeout =
|
|
default_timeout << COMPACT_MAX_DEFER_SHIFT;
|
|
}
|
|
if (unlikely(pgdat->proactive_compact_trigger))
|
|
pgdat->proactive_compact_trigger = false;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* This kcompactd start function will be called by init and node-hot-add.
|
|
* On node-hot-add, kcompactd will moved to proper cpus if cpus are hot-added.
|
|
*/
|
|
int kcompactd_run(int nid)
|
|
{
|
|
pg_data_t *pgdat = NODE_DATA(nid);
|
|
int ret = 0;
|
|
|
|
if (pgdat->kcompactd)
|
|
return 0;
|
|
|
|
pgdat->kcompactd = kthread_run(kcompactd, pgdat, "kcompactd%d", nid);
|
|
if (IS_ERR(pgdat->kcompactd)) {
|
|
pr_err("Failed to start kcompactd on node %d\n", nid);
|
|
ret = PTR_ERR(pgdat->kcompactd);
|
|
pgdat->kcompactd = NULL;
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Called by memory hotplug when all memory in a node is offlined. Caller must
|
|
* hold mem_hotplug_begin/end().
|
|
*/
|
|
void kcompactd_stop(int nid)
|
|
{
|
|
struct task_struct *kcompactd = NODE_DATA(nid)->kcompactd;
|
|
|
|
if (kcompactd) {
|
|
kthread_stop(kcompactd);
|
|
NODE_DATA(nid)->kcompactd = NULL;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* It's optimal to keep kcompactd on the same CPUs as their memory, but
|
|
* not required for correctness. So if the last cpu in a node goes
|
|
* away, we get changed to run anywhere: as the first one comes back,
|
|
* restore their cpu bindings.
|
|
*/
|
|
static int kcompactd_cpu_online(unsigned int cpu)
|
|
{
|
|
int nid;
|
|
|
|
for_each_node_state(nid, N_MEMORY) {
|
|
pg_data_t *pgdat = NODE_DATA(nid);
|
|
const struct cpumask *mask;
|
|
|
|
mask = cpumask_of_node(pgdat->node_id);
|
|
|
|
if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
|
|
/* One of our CPUs online: restore mask */
|
|
set_cpus_allowed_ptr(pgdat->kcompactd, mask);
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static int __init kcompactd_init(void)
|
|
{
|
|
int nid;
|
|
int ret;
|
|
|
|
ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
|
|
"mm/compaction:online",
|
|
kcompactd_cpu_online, NULL);
|
|
if (ret < 0) {
|
|
pr_err("kcompactd: failed to register hotplug callbacks.\n");
|
|
return ret;
|
|
}
|
|
|
|
for_each_node_state(nid, N_MEMORY)
|
|
kcompactd_run(nid);
|
|
return 0;
|
|
}
|
|
subsys_initcall(kcompactd_init)
|
|
|
|
#endif /* CONFIG_COMPACTION */
|