mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-11-14 15:54:15 +08:00
7546934570
This patch uses is_via_compact_memory() to distinguish compaction from sysfs or sysctl. And, this patch also reduces indentation on compaction_defer_reset() by filtering these cases first before checking watermark. There is no functional change. Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Acked-by: Yaowei Bai <baiyaowei@cmss.chinamobile.com> Acked-by: David Rientjes <rientjes@google.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1763 lines
48 KiB
C
1763 lines
48 KiB
C
/*
|
|
* linux/mm/compaction.c
|
|
*
|
|
* Memory compaction for the reduction of external fragmentation. Note that
|
|
* this heavily depends upon page migration to do all the real heavy
|
|
* lifting
|
|
*
|
|
* Copyright IBM Corp. 2007-2010 Mel Gorman <mel@csn.ul.ie>
|
|
*/
|
|
#include <linux/swap.h>
|
|
#include <linux/migrate.h>
|
|
#include <linux/compaction.h>
|
|
#include <linux/mm_inline.h>
|
|
#include <linux/backing-dev.h>
|
|
#include <linux/sysctl.h>
|
|
#include <linux/sysfs.h>
|
|
#include <linux/balloon_compaction.h>
|
|
#include <linux/page-isolation.h>
|
|
#include <linux/kasan.h>
|
|
#include "internal.h"
|
|
|
|
#ifdef CONFIG_COMPACTION
|
|
static inline void count_compact_event(enum vm_event_item item)
|
|
{
|
|
count_vm_event(item);
|
|
}
|
|
|
|
static inline void count_compact_events(enum vm_event_item item, long delta)
|
|
{
|
|
count_vm_events(item, delta);
|
|
}
|
|
#else
|
|
#define count_compact_event(item) do { } while (0)
|
|
#define count_compact_events(item, delta) do { } while (0)
|
|
#endif
|
|
|
|
#if defined CONFIG_COMPACTION || defined CONFIG_CMA
|
|
|
|
#define CREATE_TRACE_POINTS
|
|
#include <trace/events/compaction.h>
|
|
|
|
static unsigned long release_freepages(struct list_head *freelist)
|
|
{
|
|
struct page *page, *next;
|
|
unsigned long high_pfn = 0;
|
|
|
|
list_for_each_entry_safe(page, next, freelist, lru) {
|
|
unsigned long pfn = page_to_pfn(page);
|
|
list_del(&page->lru);
|
|
__free_page(page);
|
|
if (pfn > high_pfn)
|
|
high_pfn = pfn;
|
|
}
|
|
|
|
return high_pfn;
|
|
}
|
|
|
|
static void map_pages(struct list_head *list)
|
|
{
|
|
struct page *page;
|
|
|
|
list_for_each_entry(page, list, lru) {
|
|
arch_alloc_page(page, 0);
|
|
kernel_map_pages(page, 1, 1);
|
|
kasan_alloc_pages(page, 0);
|
|
}
|
|
}
|
|
|
|
static inline bool migrate_async_suitable(int migratetype)
|
|
{
|
|
return is_migrate_cma(migratetype) || migratetype == MIGRATE_MOVABLE;
|
|
}
|
|
|
|
/*
|
|
* Check that the whole (or subset of) a pageblock given by the interval of
|
|
* [start_pfn, end_pfn) is valid and within the same zone, before scanning it
|
|
* with the migration of free compaction scanner. The scanners then need to
|
|
* use only pfn_valid_within() check for arches that allow holes within
|
|
* pageblocks.
|
|
*
|
|
* Return struct page pointer of start_pfn, or NULL if checks were not passed.
|
|
*
|
|
* It's possible on some configurations to have a setup like node0 node1 node0
|
|
* i.e. it's possible that all pages within a zones range of pages do not
|
|
* belong to a single zone. We assume that a border between node0 and node1
|
|
* can occur within a single pageblock, but not a node0 node1 node0
|
|
* interleaving within a single pageblock. It is therefore sufficient to check
|
|
* the first and last page of a pageblock and avoid checking each individual
|
|
* page in a pageblock.
|
|
*/
|
|
static struct page *pageblock_pfn_to_page(unsigned long start_pfn,
|
|
unsigned long end_pfn, struct zone *zone)
|
|
{
|
|
struct page *start_page;
|
|
struct page *end_page;
|
|
|
|
/* end_pfn is one past the range we are checking */
|
|
end_pfn--;
|
|
|
|
if (!pfn_valid(start_pfn) || !pfn_valid(end_pfn))
|
|
return NULL;
|
|
|
|
start_page = pfn_to_page(start_pfn);
|
|
|
|
if (page_zone(start_page) != zone)
|
|
return NULL;
|
|
|
|
end_page = pfn_to_page(end_pfn);
|
|
|
|
/* This gives a shorter code than deriving page_zone(end_page) */
|
|
if (page_zone_id(start_page) != page_zone_id(end_page))
|
|
return NULL;
|
|
|
|
return start_page;
|
|
}
|
|
|
|
#ifdef CONFIG_COMPACTION
|
|
|
|
/* Do not skip compaction more than 64 times */
|
|
#define COMPACT_MAX_DEFER_SHIFT 6
|
|
|
|
/*
|
|
* Compaction is deferred when compaction fails to result in a page
|
|
* allocation success. 1 << compact_defer_limit compactions are skipped up
|
|
* to a limit of 1 << COMPACT_MAX_DEFER_SHIFT
|
|
*/
|
|
void defer_compaction(struct zone *zone, int order)
|
|
{
|
|
zone->compact_considered = 0;
|
|
zone->compact_defer_shift++;
|
|
|
|
if (order < zone->compact_order_failed)
|
|
zone->compact_order_failed = order;
|
|
|
|
if (zone->compact_defer_shift > COMPACT_MAX_DEFER_SHIFT)
|
|
zone->compact_defer_shift = COMPACT_MAX_DEFER_SHIFT;
|
|
|
|
trace_mm_compaction_defer_compaction(zone, order);
|
|
}
|
|
|
|
/* Returns true if compaction should be skipped this time */
|
|
bool compaction_deferred(struct zone *zone, int order)
|
|
{
|
|
unsigned long defer_limit = 1UL << zone->compact_defer_shift;
|
|
|
|
if (order < zone->compact_order_failed)
|
|
return false;
|
|
|
|
/* Avoid possible overflow */
|
|
if (++zone->compact_considered > defer_limit)
|
|
zone->compact_considered = defer_limit;
|
|
|
|
if (zone->compact_considered >= defer_limit)
|
|
return false;
|
|
|
|
trace_mm_compaction_deferred(zone, order);
|
|
|
|
return true;
|
|
}
|
|
|
|
/*
|
|
* Update defer tracking counters after successful compaction of given order,
|
|
* which means an allocation either succeeded (alloc_success == true) or is
|
|
* expected to succeed.
|
|
*/
|
|
void compaction_defer_reset(struct zone *zone, int order,
|
|
bool alloc_success)
|
|
{
|
|
if (alloc_success) {
|
|
zone->compact_considered = 0;
|
|
zone->compact_defer_shift = 0;
|
|
}
|
|
if (order >= zone->compact_order_failed)
|
|
zone->compact_order_failed = order + 1;
|
|
|
|
trace_mm_compaction_defer_reset(zone, order);
|
|
}
|
|
|
|
/* Returns true if restarting compaction after many failures */
|
|
bool compaction_restarting(struct zone *zone, int order)
|
|
{
|
|
if (order < zone->compact_order_failed)
|
|
return false;
|
|
|
|
return zone->compact_defer_shift == COMPACT_MAX_DEFER_SHIFT &&
|
|
zone->compact_considered >= 1UL << zone->compact_defer_shift;
|
|
}
|
|
|
|
/* Returns true if the pageblock should be scanned for pages to isolate. */
|
|
static inline bool isolation_suitable(struct compact_control *cc,
|
|
struct page *page)
|
|
{
|
|
if (cc->ignore_skip_hint)
|
|
return true;
|
|
|
|
return !get_pageblock_skip(page);
|
|
}
|
|
|
|
static void reset_cached_positions(struct zone *zone)
|
|
{
|
|
zone->compact_cached_migrate_pfn[0] = zone->zone_start_pfn;
|
|
zone->compact_cached_migrate_pfn[1] = zone->zone_start_pfn;
|
|
zone->compact_cached_free_pfn = zone_end_pfn(zone);
|
|
}
|
|
|
|
/*
|
|
* This function is called to clear all cached information on pageblocks that
|
|
* should be skipped for page isolation when the migrate and free page scanner
|
|
* meet.
|
|
*/
|
|
static void __reset_isolation_suitable(struct zone *zone)
|
|
{
|
|
unsigned long start_pfn = zone->zone_start_pfn;
|
|
unsigned long end_pfn = zone_end_pfn(zone);
|
|
unsigned long pfn;
|
|
|
|
zone->compact_blockskip_flush = false;
|
|
|
|
/* Walk the zone and mark every pageblock as suitable for isolation */
|
|
for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
|
|
struct page *page;
|
|
|
|
cond_resched();
|
|
|
|
if (!pfn_valid(pfn))
|
|
continue;
|
|
|
|
page = pfn_to_page(pfn);
|
|
if (zone != page_zone(page))
|
|
continue;
|
|
|
|
clear_pageblock_skip(page);
|
|
}
|
|
|
|
reset_cached_positions(zone);
|
|
}
|
|
|
|
void reset_isolation_suitable(pg_data_t *pgdat)
|
|
{
|
|
int zoneid;
|
|
|
|
for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
|
|
struct zone *zone = &pgdat->node_zones[zoneid];
|
|
if (!populated_zone(zone))
|
|
continue;
|
|
|
|
/* Only flush if a full compaction finished recently */
|
|
if (zone->compact_blockskip_flush)
|
|
__reset_isolation_suitable(zone);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* If no pages were isolated then mark this pageblock to be skipped in the
|
|
* future. The information is later cleared by __reset_isolation_suitable().
|
|
*/
|
|
static void update_pageblock_skip(struct compact_control *cc,
|
|
struct page *page, unsigned long nr_isolated,
|
|
bool migrate_scanner)
|
|
{
|
|
struct zone *zone = cc->zone;
|
|
unsigned long pfn;
|
|
|
|
if (cc->ignore_skip_hint)
|
|
return;
|
|
|
|
if (!page)
|
|
return;
|
|
|
|
if (nr_isolated)
|
|
return;
|
|
|
|
set_pageblock_skip(page);
|
|
|
|
pfn = page_to_pfn(page);
|
|
|
|
/* Update where async and sync compaction should restart */
|
|
if (migrate_scanner) {
|
|
if (pfn > zone->compact_cached_migrate_pfn[0])
|
|
zone->compact_cached_migrate_pfn[0] = pfn;
|
|
if (cc->mode != MIGRATE_ASYNC &&
|
|
pfn > zone->compact_cached_migrate_pfn[1])
|
|
zone->compact_cached_migrate_pfn[1] = pfn;
|
|
} else {
|
|
if (pfn < zone->compact_cached_free_pfn)
|
|
zone->compact_cached_free_pfn = pfn;
|
|
}
|
|
}
|
|
#else
|
|
static inline bool isolation_suitable(struct compact_control *cc,
|
|
struct page *page)
|
|
{
|
|
return true;
|
|
}
|
|
|
|
static void update_pageblock_skip(struct compact_control *cc,
|
|
struct page *page, unsigned long nr_isolated,
|
|
bool migrate_scanner)
|
|
{
|
|
}
|
|
#endif /* CONFIG_COMPACTION */
|
|
|
|
/*
|
|
* Compaction requires the taking of some coarse locks that are potentially
|
|
* very heavily contended. For async compaction, back out if the lock cannot
|
|
* be taken immediately. For sync compaction, spin on the lock if needed.
|
|
*
|
|
* Returns true if the lock is held
|
|
* Returns false if the lock is not held and compaction should abort
|
|
*/
|
|
static bool compact_trylock_irqsave(spinlock_t *lock, unsigned long *flags,
|
|
struct compact_control *cc)
|
|
{
|
|
if (cc->mode == MIGRATE_ASYNC) {
|
|
if (!spin_trylock_irqsave(lock, *flags)) {
|
|
cc->contended = COMPACT_CONTENDED_LOCK;
|
|
return false;
|
|
}
|
|
} else {
|
|
spin_lock_irqsave(lock, *flags);
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
/*
|
|
* 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 = COMPACT_CONTENDED_SCHED;
|
|
return true;
|
|
}
|
|
|
|
if (need_resched()) {
|
|
if (cc->mode == MIGRATE_ASYNC) {
|
|
cc->contended = COMPACT_CONTENDED_SCHED;
|
|
return true;
|
|
}
|
|
cond_resched();
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
/*
|
|
* Aside from avoiding lock contention, compaction also periodically checks
|
|
* need_resched() and either schedules in sync compaction or aborts async
|
|
* compaction. This is similar to what compact_unlock_should_abort() does, but
|
|
* is used where no lock is concerned.
|
|
*
|
|
* Returns false when no scheduling was needed, or sync compaction scheduled.
|
|
* Returns true when async compaction should abort.
|
|
*/
|
|
static inline bool compact_should_abort(struct compact_control *cc)
|
|
{
|
|
/* async compaction aborts if contended */
|
|
if (need_resched()) {
|
|
if (cc->mode == MIGRATE_ASYNC) {
|
|
cc->contended = COMPACT_CONTENDED_SCHED;
|
|
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,
|
|
bool strict)
|
|
{
|
|
int nr_scanned = 0, total_isolated = 0;
|
|
struct page *cursor, *valid_page = NULL;
|
|
unsigned long flags = 0;
|
|
bool locked = false;
|
|
unsigned long blockpfn = *start_pfn;
|
|
|
|
cursor = pfn_to_page(blockpfn);
|
|
|
|
/* Isolate free pages. */
|
|
for (; blockpfn < end_pfn; blockpfn++, cursor++) {
|
|
int isolated, i;
|
|
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++;
|
|
if (!pfn_valid_within(blockpfn))
|
|
goto isolate_fail;
|
|
|
|
if (!valid_page)
|
|
valid_page = page;
|
|
|
|
/*
|
|
* 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)) {
|
|
unsigned int comp_order = compound_order(page);
|
|
|
|
if (likely(comp_order < MAX_ORDER)) {
|
|
blockpfn += (1UL << comp_order) - 1;
|
|
cursor += (1UL << comp_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) {
|
|
/*
|
|
* The zone lock must be held to isolate freepages.
|
|
* Unfortunately this is a very coarse lock and can be
|
|
* heavily contended if there are parallel allocations
|
|
* or parallel compactions. For async compaction do not
|
|
* spin on the lock and we acquire the lock as late as
|
|
* possible.
|
|
*/
|
|
locked = compact_trylock_irqsave(&cc->zone->lock,
|
|
&flags, cc);
|
|
if (!locked)
|
|
break;
|
|
|
|
/* Recheck this is a buddy page under lock */
|
|
if (!PageBuddy(page))
|
|
goto isolate_fail;
|
|
}
|
|
|
|
/* Found a free page, break it into order-0 pages */
|
|
isolated = split_free_page(page);
|
|
total_isolated += isolated;
|
|
for (i = 0; i < isolated; i++) {
|
|
list_add(&page->lru, freelist);
|
|
page++;
|
|
}
|
|
|
|
/* If a page was split, advance to the end of it */
|
|
if (isolated) {
|
|
cc->nr_freepages += isolated;
|
|
if (!strict &&
|
|
cc->nr_migratepages <= cc->nr_freepages) {
|
|
blockpfn += isolated;
|
|
break;
|
|
}
|
|
|
|
blockpfn += isolated - 1;
|
|
cursor += isolated - 1;
|
|
continue;
|
|
}
|
|
|
|
isolate_fail:
|
|
if (strict)
|
|
break;
|
|
else
|
|
continue;
|
|
|
|
}
|
|
|
|
/*
|
|
* 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;
|
|
|
|
if (locked)
|
|
spin_unlock_irqrestore(&cc->zone->lock, flags);
|
|
|
|
/* Update the pageblock-skip if the whole pageblock was scanned */
|
|
if (blockpfn == end_pfn)
|
|
update_pageblock_skip(cc, valid_page, total_isolated, false);
|
|
|
|
count_compact_events(COMPACTFREE_SCANNED, nr_scanned);
|
|
if (total_isolated)
|
|
count_compact_events(COMPACTISOLATED, total_isolated);
|
|
return total_isolated;
|
|
}
|
|
|
|
/**
|
|
* isolate_freepages_range() - isolate free pages.
|
|
* @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_end_pfn;
|
|
LIST_HEAD(freelist);
|
|
|
|
pfn = start_pfn;
|
|
block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
|
|
|
|
for (; pfn < end_pfn; pfn += isolated,
|
|
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_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
|
|
block_end_pfn = min(block_end_pfn, end_pfn);
|
|
}
|
|
|
|
if (!pageblock_pfn_to_page(pfn, block_end_pfn, cc->zone))
|
|
break;
|
|
|
|
isolated = isolate_freepages_block(cc, &isolate_start_pfn,
|
|
block_end_pfn, &freelist, 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).
|
|
*/
|
|
}
|
|
|
|
/* split_free_page does not map the pages */
|
|
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;
|
|
}
|
|
|
|
/* Update the number of anon and file isolated pages in the zone */
|
|
static void acct_isolated(struct zone *zone, struct compact_control *cc)
|
|
{
|
|
struct page *page;
|
|
unsigned int count[2] = { 0, };
|
|
|
|
if (list_empty(&cc->migratepages))
|
|
return;
|
|
|
|
list_for_each_entry(page, &cc->migratepages, lru)
|
|
count[!!page_is_file_cache(page)]++;
|
|
|
|
mod_zone_page_state(zone, NR_ISOLATED_ANON, count[0]);
|
|
mod_zone_page_state(zone, NR_ISOLATED_FILE, count[1]);
|
|
}
|
|
|
|
/* Similar to reclaim, but different enough that they don't share logic */
|
|
static bool too_many_isolated(struct zone *zone)
|
|
{
|
|
unsigned long active, inactive, isolated;
|
|
|
|
inactive = zone_page_state(zone, NR_INACTIVE_FILE) +
|
|
zone_page_state(zone, NR_INACTIVE_ANON);
|
|
active = zone_page_state(zone, NR_ACTIVE_FILE) +
|
|
zone_page_state(zone, NR_ACTIVE_ANON);
|
|
isolated = zone_page_state(zone, NR_ISOLATED_FILE) +
|
|
zone_page_state(zone, NR_ISOLATED_ANON);
|
|
|
|
return isolated > (inactive + active) / 2;
|
|
}
|
|
|
|
/**
|
|
* 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
|
|
* @isolate_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 zero if there is a fatal signal pending, otherwise PFN of the
|
|
* first page that was not scanned (which may be both less, equal to or more
|
|
* than end_pfn).
|
|
*
|
|
* The pages are isolated on cc->migratepages list (not required to be empty),
|
|
* and cc->nr_migratepages is updated accordingly. The cc->migrate_pfn field
|
|
* is neither read nor updated.
|
|
*/
|
|
static unsigned long
|
|
isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
|
|
unsigned long end_pfn, isolate_mode_t isolate_mode)
|
|
{
|
|
struct zone *zone = cc->zone;
|
|
unsigned long nr_scanned = 0, nr_isolated = 0;
|
|
struct list_head *migratelist = &cc->migratepages;
|
|
struct lruvec *lruvec;
|
|
unsigned long flags = 0;
|
|
bool locked = false;
|
|
struct page *page = NULL, *valid_page = NULL;
|
|
unsigned long start_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(zone))) {
|
|
/* async migration should just abort */
|
|
if (cc->mode == MIGRATE_ASYNC)
|
|
return 0;
|
|
|
|
congestion_wait(BLK_RW_ASYNC, HZ/10);
|
|
|
|
if (fatal_signal_pending(current))
|
|
return 0;
|
|
}
|
|
|
|
if (compact_should_abort(cc))
|
|
return 0;
|
|
|
|
/* Time to isolate some pages for migration */
|
|
for (; low_pfn < end_pfn; low_pfn++) {
|
|
bool is_lru;
|
|
|
|
/*
|
|
* Periodically drop the lock (if held) regardless of its
|
|
* contention, to give chance to IRQs. Abort async compaction
|
|
* if contended.
|
|
*/
|
|
if (!(low_pfn % SWAP_CLUSTER_MAX)
|
|
&& compact_unlock_should_abort(&zone->lru_lock, flags,
|
|
&locked, cc))
|
|
break;
|
|
|
|
if (!pfn_valid_within(low_pfn))
|
|
continue;
|
|
nr_scanned++;
|
|
|
|
page = pfn_to_page(low_pfn);
|
|
|
|
if (!valid_page)
|
|
valid_page = page;
|
|
|
|
/*
|
|
* 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 = page_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;
|
|
}
|
|
|
|
/*
|
|
* Check may be lockless but that's ok as we recheck later.
|
|
* It's possible to migrate LRU pages and balloon pages
|
|
* Skip any other type of page
|
|
*/
|
|
is_lru = PageLRU(page);
|
|
if (!is_lru) {
|
|
if (unlikely(balloon_page_movable(page))) {
|
|
if (balloon_page_isolate(page)) {
|
|
/* Successfully isolated */
|
|
goto isolate_success;
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Regardless of being on LRU, compound pages such as THP and
|
|
* hugetlbfs are not to be compacted. 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)) {
|
|
unsigned int comp_order = compound_order(page);
|
|
|
|
if (likely(comp_order < MAX_ORDER))
|
|
low_pfn += (1UL << comp_order) - 1;
|
|
|
|
continue;
|
|
}
|
|
|
|
if (!is_lru)
|
|
continue;
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
if (!page_mapping(page) &&
|
|
page_count(page) > page_mapcount(page))
|
|
continue;
|
|
|
|
/* If we already hold the lock, we can skip some rechecking */
|
|
if (!locked) {
|
|
locked = compact_trylock_irqsave(&zone->lru_lock,
|
|
&flags, cc);
|
|
if (!locked)
|
|
break;
|
|
|
|
/* Recheck PageLRU and PageCompound under lock */
|
|
if (!PageLRU(page))
|
|
continue;
|
|
|
|
/*
|
|
* 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))) {
|
|
low_pfn += (1UL << compound_order(page)) - 1;
|
|
continue;
|
|
}
|
|
}
|
|
|
|
lruvec = mem_cgroup_page_lruvec(page, zone);
|
|
|
|
/* Try isolate the page */
|
|
if (__isolate_lru_page(page, isolate_mode) != 0)
|
|
continue;
|
|
|
|
VM_BUG_ON_PAGE(PageCompound(page), page);
|
|
|
|
/* Successfully isolated */
|
|
del_page_from_lru_list(page, lruvec, page_lru(page));
|
|
|
|
isolate_success:
|
|
list_add(&page->lru, migratelist);
|
|
cc->nr_migratepages++;
|
|
nr_isolated++;
|
|
|
|
/* Avoid isolating too much */
|
|
if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) {
|
|
++low_pfn;
|
|
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;
|
|
|
|
if (locked)
|
|
spin_unlock_irqrestore(&zone->lru_lock, flags);
|
|
|
|
/*
|
|
* Update the pageblock-skip information and cached scanner pfn,
|
|
* if the whole pageblock was scanned without isolating any page.
|
|
*/
|
|
if (low_pfn == end_pfn)
|
|
update_pageblock_skip(cc, valid_page, nr_isolated, true);
|
|
|
|
trace_mm_compaction_isolate_migratepages(start_pfn, low_pfn,
|
|
nr_scanned, nr_isolated);
|
|
|
|
count_compact_events(COMPACTMIGRATE_SCANNED, nr_scanned);
|
|
if (nr_isolated)
|
|
count_compact_events(COMPACTISOLATED, nr_isolated);
|
|
|
|
return low_pfn;
|
|
}
|
|
|
|
/**
|
|
* 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 zero if isolation fails fatally due to e.g. pending signal.
|
|
* Otherwise, function returns one-past-the-last PFN of isolated page
|
|
* (which may be greater than end_pfn if end fell in a middle of a THP page).
|
|
*/
|
|
unsigned long
|
|
isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn,
|
|
unsigned long end_pfn)
|
|
{
|
|
unsigned long pfn, block_end_pfn;
|
|
|
|
/* Scan block by block. First and last block may be incomplete */
|
|
pfn = start_pfn;
|
|
block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
|
|
|
|
for (; pfn < end_pfn; pfn = block_end_pfn,
|
|
block_end_pfn += pageblock_nr_pages) {
|
|
|
|
block_end_pfn = min(block_end_pfn, end_pfn);
|
|
|
|
if (!pageblock_pfn_to_page(pfn, block_end_pfn, cc->zone))
|
|
continue;
|
|
|
|
pfn = isolate_migratepages_block(cc, pfn, block_end_pfn,
|
|
ISOLATE_UNEVICTABLE);
|
|
|
|
/*
|
|
* In case of fatal failure, release everything that might
|
|
* have been isolated in the previous iteration, and signal
|
|
* the failure back to caller.
|
|
*/
|
|
if (!pfn) {
|
|
putback_movable_pages(&cc->migratepages);
|
|
cc->nr_migratepages = 0;
|
|
break;
|
|
}
|
|
|
|
if (cc->nr_migratepages == COMPACT_CLUSTER_MAX)
|
|
break;
|
|
}
|
|
acct_isolated(cc->zone, cc);
|
|
|
|
return pfn;
|
|
}
|
|
|
|
#endif /* CONFIG_COMPACTION || CONFIG_CMA */
|
|
#ifdef CONFIG_COMPACTION
|
|
|
|
/* Returns true if the page is within a block suitable for migration to */
|
|
static bool suitable_migration_target(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 (page_order_unsafe(page) >= pageblock_order)
|
|
return false;
|
|
}
|
|
|
|
/* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
|
|
if (migrate_async_suitable(get_pageblock_migratetype(page)))
|
|
return true;
|
|
|
|
/* Otherwise skip the block */
|
|
return false;
|
|
}
|
|
|
|
/*
|
|
* 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);
|
|
}
|
|
|
|
/*
|
|
* 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;
|
|
|
|
/*
|
|
* 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
|
|
* 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 = cc->free_pfn & ~(pageblock_nr_pages-1);
|
|
block_end_pfn = min(block_start_pfn + pageblock_nr_pages,
|
|
zone_end_pfn(zone));
|
|
low_pfn = ALIGN(cc->migrate_pfn + 1, pageblock_nr_pages);
|
|
|
|
/*
|
|
* 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) {
|
|
|
|
/*
|
|
* This can iterate a massively long zone without finding any
|
|
* suitable migration targets, so periodically check if we need
|
|
* to schedule, or even abort async compaction.
|
|
*/
|
|
if (!(block_start_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages))
|
|
&& compact_should_abort(cc))
|
|
break;
|
|
|
|
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(page))
|
|
continue;
|
|
|
|
/* If isolation recently failed, do not retry */
|
|
if (!isolation_suitable(cc, page))
|
|
continue;
|
|
|
|
/* Found a block suitable for isolating free pages from. */
|
|
isolate_freepages_block(cc, &isolate_start_pfn,
|
|
block_end_pfn, freelist, false);
|
|
|
|
/*
|
|
* If we isolated enough freepages, or aborted due to async
|
|
* compaction being contended, terminate the loop.
|
|
* Remember where the free scanner should restart next time,
|
|
* which is where isolate_freepages_block() left off.
|
|
* But if it scanned the whole pageblock, isolate_start_pfn
|
|
* now points at block_end_pfn, which is the start of the next
|
|
* pageblock.
|
|
* In that case we will however want to restart at the start
|
|
* of the previous pageblock.
|
|
*/
|
|
if ((cc->nr_freepages >= cc->nr_migratepages)
|
|
|| cc->contended) {
|
|
if (isolate_start_pfn >= block_end_pfn)
|
|
isolate_start_pfn =
|
|
block_start_pfn - pageblock_nr_pages;
|
|
break;
|
|
} else {
|
|
/*
|
|
* isolate_freepages_block() should not terminate
|
|
* prematurely unless contended, or isolated enough
|
|
*/
|
|
VM_BUG_ON(isolate_start_pfn < block_end_pfn);
|
|
}
|
|
}
|
|
|
|
/* split_free_page does not map the pages */
|
|
map_pages(freelist);
|
|
|
|
/*
|
|
* 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;
|
|
}
|
|
|
|
/*
|
|
* 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,
|
|
int **result)
|
|
{
|
|
struct compact_control *cc = (struct compact_control *)data;
|
|
struct page *freepage;
|
|
|
|
/*
|
|
* Isolate free pages if necessary, and if we are not aborting due to
|
|
* contention.
|
|
*/
|
|
if (list_empty(&cc->freepages)) {
|
|
if (!cc->contended)
|
|
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.
|
|
*/
|
|
int sysctl_compact_unevictable_allowed __read_mostly = 1;
|
|
|
|
/*
|
|
* 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 zone *zone,
|
|
struct compact_control *cc)
|
|
{
|
|
unsigned long low_pfn, end_pfn;
|
|
unsigned long isolate_start_pfn;
|
|
struct page *page;
|
|
const isolate_mode_t isolate_mode =
|
|
(sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) |
|
|
(cc->mode == MIGRATE_ASYNC ? ISOLATE_ASYNC_MIGRATE : 0);
|
|
|
|
/*
|
|
* Start at where we last stopped, or beginning of the zone as
|
|
* initialized by compact_zone()
|
|
*/
|
|
low_pfn = cc->migrate_pfn;
|
|
|
|
/* Only scan within a pageblock boundary */
|
|
end_pfn = ALIGN(low_pfn + 1, pageblock_nr_pages);
|
|
|
|
/*
|
|
* Iterate over whole pageblocks until we find the first suitable.
|
|
* Do not cross the free scanner.
|
|
*/
|
|
for (; end_pfn <= cc->free_pfn;
|
|
low_pfn = end_pfn, 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, or even abort async compaction.
|
|
*/
|
|
if (!(low_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages))
|
|
&& compact_should_abort(cc))
|
|
break;
|
|
|
|
page = pageblock_pfn_to_page(low_pfn, end_pfn, zone);
|
|
if (!page)
|
|
continue;
|
|
|
|
/* If isolation recently failed, do not retry */
|
|
if (!isolation_suitable(cc, page))
|
|
continue;
|
|
|
|
/*
|
|
* For async compaction, also only scan in MOVABLE blocks.
|
|
* Async compaction is optimistic to see if the minimum amount
|
|
* of work satisfies the allocation.
|
|
*/
|
|
if (cc->mode == MIGRATE_ASYNC &&
|
|
!migrate_async_suitable(get_pageblock_migratetype(page)))
|
|
continue;
|
|
|
|
/* Perform the isolation */
|
|
isolate_start_pfn = low_pfn;
|
|
low_pfn = isolate_migratepages_block(cc, low_pfn, end_pfn,
|
|
isolate_mode);
|
|
|
|
if (!low_pfn || cc->contended) {
|
|
acct_isolated(zone, cc);
|
|
return ISOLATE_ABORT;
|
|
}
|
|
|
|
/*
|
|
* Record where we could have freed pages by migration and not
|
|
* yet flushed them to buddy allocator.
|
|
* - this is the lowest page that could have been isolated and
|
|
* then freed by migration.
|
|
*/
|
|
if (cc->nr_migratepages && !cc->last_migrated_pfn)
|
|
cc->last_migrated_pfn = isolate_start_pfn;
|
|
|
|
/*
|
|
* Either we isolated something and proceed with migration. Or
|
|
* we failed and compact_zone should decide if we should
|
|
* continue or not.
|
|
*/
|
|
break;
|
|
}
|
|
|
|
acct_isolated(zone, cc);
|
|
/* Record where migration scanner will be restarted. */
|
|
cc->migrate_pfn = low_pfn;
|
|
|
|
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 int __compact_finished(struct zone *zone, struct compact_control *cc,
|
|
const int migratetype)
|
|
{
|
|
unsigned int order;
|
|
unsigned long watermark;
|
|
|
|
if (cc->contended || fatal_signal_pending(current))
|
|
return COMPACT_CONTENDED;
|
|
|
|
/* Compaction run completes if the migrate and free scanner meet */
|
|
if (compact_scanners_met(cc)) {
|
|
/* Let the next compaction start anew. */
|
|
reset_cached_positions(zone);
|
|
|
|
/*
|
|
* Mark that the PG_migrate_skip information should be cleared
|
|
* by kswapd when it goes to sleep. kswapd does not set the
|
|
* flag itself as the decision to be clear should be directly
|
|
* based on an allocation request.
|
|
*/
|
|
if (!current_is_kswapd())
|
|
zone->compact_blockskip_flush = true;
|
|
|
|
return COMPACT_COMPLETE;
|
|
}
|
|
|
|
if (is_via_compact_memory(cc->order))
|
|
return COMPACT_CONTINUE;
|
|
|
|
/* Compaction run is not finished if the watermark is not met */
|
|
watermark = low_wmark_pages(zone);
|
|
|
|
if (!zone_watermark_ok(zone, cc->order, watermark, cc->classzone_idx,
|
|
cc->alloc_flags))
|
|
return COMPACT_CONTINUE;
|
|
|
|
/* Direct compactor: Is a suitable page free? */
|
|
for (order = cc->order; order < MAX_ORDER; order++) {
|
|
struct free_area *area = &zone->free_area[order];
|
|
bool can_steal;
|
|
|
|
/* Job done if page is free of the right migratetype */
|
|
if (!list_empty(&area->free_list[migratetype]))
|
|
return COMPACT_PARTIAL;
|
|
|
|
#ifdef CONFIG_CMA
|
|
/* MIGRATE_MOVABLE can fallback on MIGRATE_CMA */
|
|
if (migratetype == MIGRATE_MOVABLE &&
|
|
!list_empty(&area->free_list[MIGRATE_CMA]))
|
|
return COMPACT_PARTIAL;
|
|
#endif
|
|
/*
|
|
* Job done if allocation would steal freepages from
|
|
* other migratetype buddy lists.
|
|
*/
|
|
if (find_suitable_fallback(area, order, migratetype,
|
|
true, &can_steal) != -1)
|
|
return COMPACT_PARTIAL;
|
|
}
|
|
|
|
return COMPACT_NO_SUITABLE_PAGE;
|
|
}
|
|
|
|
static int compact_finished(struct zone *zone, struct compact_control *cc,
|
|
const int migratetype)
|
|
{
|
|
int ret;
|
|
|
|
ret = __compact_finished(zone, cc, migratetype);
|
|
trace_mm_compaction_finished(zone, cc->order, ret);
|
|
if (ret == COMPACT_NO_SUITABLE_PAGE)
|
|
ret = COMPACT_CONTINUE;
|
|
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* 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_PARTIAL - If the allocation would succeed without compaction
|
|
* COMPACT_CONTINUE - If compaction should run now
|
|
*/
|
|
static unsigned long __compaction_suitable(struct zone *zone, int order,
|
|
int alloc_flags, int classzone_idx)
|
|
{
|
|
int fragindex;
|
|
unsigned long watermark;
|
|
|
|
if (is_via_compact_memory(order))
|
|
return COMPACT_CONTINUE;
|
|
|
|
watermark = low_wmark_pages(zone);
|
|
/*
|
|
* 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, classzone_idx,
|
|
alloc_flags))
|
|
return COMPACT_PARTIAL;
|
|
|
|
/*
|
|
* Watermarks for order-0 must be met for compaction. Note the 2UL.
|
|
* This is because during migration, copies of pages need to be
|
|
* allocated and for a short time, the footprint is higher
|
|
*/
|
|
watermark += (2UL << order);
|
|
if (!zone_watermark_ok(zone, 0, watermark, classzone_idx, alloc_flags))
|
|
return COMPACT_SKIPPED;
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
fragindex = fragmentation_index(zone, order);
|
|
if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
|
|
return COMPACT_NOT_SUITABLE_ZONE;
|
|
|
|
return COMPACT_CONTINUE;
|
|
}
|
|
|
|
unsigned long compaction_suitable(struct zone *zone, int order,
|
|
int alloc_flags, int classzone_idx)
|
|
{
|
|
unsigned long ret;
|
|
|
|
ret = __compaction_suitable(zone, order, alloc_flags, classzone_idx);
|
|
trace_mm_compaction_suitable(zone, order, ret);
|
|
if (ret == COMPACT_NOT_SUITABLE_ZONE)
|
|
ret = COMPACT_SKIPPED;
|
|
|
|
return ret;
|
|
}
|
|
|
|
static int compact_zone(struct zone *zone, struct compact_control *cc)
|
|
{
|
|
int ret;
|
|
unsigned long start_pfn = zone->zone_start_pfn;
|
|
unsigned long end_pfn = zone_end_pfn(zone);
|
|
const int migratetype = gfpflags_to_migratetype(cc->gfp_mask);
|
|
const bool sync = cc->mode != MIGRATE_ASYNC;
|
|
|
|
ret = compaction_suitable(zone, cc->order, cc->alloc_flags,
|
|
cc->classzone_idx);
|
|
switch (ret) {
|
|
case COMPACT_PARTIAL:
|
|
case COMPACT_SKIPPED:
|
|
/* Compaction is likely to fail */
|
|
return ret;
|
|
case COMPACT_CONTINUE:
|
|
/* Fall through to compaction */
|
|
;
|
|
}
|
|
|
|
/*
|
|
* Clear pageblock skip if there were failures recently and compaction
|
|
* is about to be retried after being deferred. kswapd does not do
|
|
* this reset as it'll reset the cached information when going to sleep.
|
|
*/
|
|
if (compaction_restarting(zone, cc->order) && !current_is_kswapd())
|
|
__reset_isolation_suitable(zone);
|
|
|
|
/*
|
|
* Setup to move all movable pages to the end of the zone. Used cached
|
|
* information on where the scanners should start but check that it
|
|
* is initialised by ensuring the values are within zone boundaries.
|
|
*/
|
|
cc->migrate_pfn = zone->compact_cached_migrate_pfn[sync];
|
|
cc->free_pfn = zone->compact_cached_free_pfn;
|
|
if (cc->free_pfn < start_pfn || cc->free_pfn > end_pfn) {
|
|
cc->free_pfn = end_pfn & ~(pageblock_nr_pages-1);
|
|
zone->compact_cached_free_pfn = cc->free_pfn;
|
|
}
|
|
if (cc->migrate_pfn < start_pfn || cc->migrate_pfn > end_pfn) {
|
|
cc->migrate_pfn = start_pfn;
|
|
zone->compact_cached_migrate_pfn[0] = cc->migrate_pfn;
|
|
zone->compact_cached_migrate_pfn[1] = cc->migrate_pfn;
|
|
}
|
|
cc->last_migrated_pfn = 0;
|
|
|
|
trace_mm_compaction_begin(start_pfn, cc->migrate_pfn,
|
|
cc->free_pfn, end_pfn, sync);
|
|
|
|
migrate_prep_local();
|
|
|
|
while ((ret = compact_finished(zone, cc, migratetype)) ==
|
|
COMPACT_CONTINUE) {
|
|
int err;
|
|
|
|
switch (isolate_migratepages(zone, cc)) {
|
|
case ISOLATE_ABORT:
|
|
ret = COMPACT_CONTENDED;
|
|
putback_movable_pages(&cc->migratepages);
|
|
cc->nr_migratepages = 0;
|
|
goto out;
|
|
case ISOLATE_NONE:
|
|
/*
|
|
* 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:
|
|
;
|
|
}
|
|
|
|
err = migrate_pages(&cc->migratepages, compaction_alloc,
|
|
compaction_free, (unsigned long)cc, cc->mode,
|
|
MR_COMPACTION);
|
|
|
|
trace_mm_compaction_migratepages(cc->nr_migratepages, err,
|
|
&cc->migratepages);
|
|
|
|
/* 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;
|
|
}
|
|
}
|
|
|
|
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 && cc->last_migrated_pfn) {
|
|
int cpu;
|
|
unsigned long current_block_start =
|
|
cc->migrate_pfn & ~((1UL << cc->order) - 1);
|
|
|
|
if (cc->last_migrated_pfn < current_block_start) {
|
|
cpu = get_cpu();
|
|
lru_add_drain_cpu(cpu);
|
|
drain_local_pages(zone);
|
|
put_cpu();
|
|
/* No more flushing until we migrate again */
|
|
cc->last_migrated_pfn = 0;
|
|
}
|
|
}
|
|
|
|
}
|
|
|
|
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_nr_pages-1);
|
|
/*
|
|
* Only go back, not forward. The cached pfn might have been
|
|
* already reset to zone end in compact_finished()
|
|
*/
|
|
if (free_pfn > zone->compact_cached_free_pfn)
|
|
zone->compact_cached_free_pfn = free_pfn;
|
|
}
|
|
|
|
trace_mm_compaction_end(start_pfn, cc->migrate_pfn,
|
|
cc->free_pfn, end_pfn, sync, ret);
|
|
|
|
if (ret == COMPACT_CONTENDED)
|
|
ret = COMPACT_PARTIAL;
|
|
|
|
return ret;
|
|
}
|
|
|
|
static unsigned long compact_zone_order(struct zone *zone, int order,
|
|
gfp_t gfp_mask, enum migrate_mode mode, int *contended,
|
|
int alloc_flags, int classzone_idx)
|
|
{
|
|
unsigned long ret;
|
|
struct compact_control cc = {
|
|
.nr_freepages = 0,
|
|
.nr_migratepages = 0,
|
|
.order = order,
|
|
.gfp_mask = gfp_mask,
|
|
.zone = zone,
|
|
.mode = mode,
|
|
.alloc_flags = alloc_flags,
|
|
.classzone_idx = classzone_idx,
|
|
};
|
|
INIT_LIST_HEAD(&cc.freepages);
|
|
INIT_LIST_HEAD(&cc.migratepages);
|
|
|
|
ret = compact_zone(zone, &cc);
|
|
|
|
VM_BUG_ON(!list_empty(&cc.freepages));
|
|
VM_BUG_ON(!list_empty(&cc.migratepages));
|
|
|
|
*contended = cc.contended;
|
|
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
|
|
* @mode: The migration mode for async, sync light, or sync migration
|
|
* @contended: Return value that determines if compaction was aborted due to
|
|
* need_resched() or lock contention
|
|
*
|
|
* This is the main entry point for direct page compaction.
|
|
*/
|
|
unsigned long try_to_compact_pages(gfp_t gfp_mask, unsigned int order,
|
|
int alloc_flags, const struct alloc_context *ac,
|
|
enum migrate_mode mode, int *contended)
|
|
{
|
|
int may_enter_fs = gfp_mask & __GFP_FS;
|
|
int may_perform_io = gfp_mask & __GFP_IO;
|
|
struct zoneref *z;
|
|
struct zone *zone;
|
|
int rc = COMPACT_DEFERRED;
|
|
int all_zones_contended = COMPACT_CONTENDED_LOCK; /* init for &= op */
|
|
|
|
*contended = COMPACT_CONTENDED_NONE;
|
|
|
|
/* Check if the GFP flags allow compaction */
|
|
if (!order || !may_enter_fs || !may_perform_io)
|
|
return COMPACT_SKIPPED;
|
|
|
|
trace_mm_compaction_try_to_compact_pages(order, gfp_mask, mode);
|
|
|
|
/* Compact each zone in the list */
|
|
for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx,
|
|
ac->nodemask) {
|
|
int status;
|
|
int zone_contended;
|
|
|
|
if (compaction_deferred(zone, order))
|
|
continue;
|
|
|
|
status = compact_zone_order(zone, order, gfp_mask, mode,
|
|
&zone_contended, alloc_flags,
|
|
ac->classzone_idx);
|
|
rc = max(status, rc);
|
|
/*
|
|
* It takes at least one zone that wasn't lock contended
|
|
* to clear all_zones_contended.
|
|
*/
|
|
all_zones_contended &= zone_contended;
|
|
|
|
/* If a normal allocation would succeed, stop compacting */
|
|
if (zone_watermark_ok(zone, order, low_wmark_pages(zone),
|
|
ac->classzone_idx, alloc_flags)) {
|
|
/*
|
|
* 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);
|
|
/*
|
|
* It is possible that async compaction aborted due to
|
|
* need_resched() and the watermarks were ok thanks to
|
|
* somebody else freeing memory. The allocation can
|
|
* however still fail so we better signal the
|
|
* need_resched() contention anyway (this will not
|
|
* prevent the allocation attempt).
|
|
*/
|
|
if (zone_contended == COMPACT_CONTENDED_SCHED)
|
|
*contended = COMPACT_CONTENDED_SCHED;
|
|
|
|
goto break_loop;
|
|
}
|
|
|
|
if (mode != MIGRATE_ASYNC && status == COMPACT_COMPLETE) {
|
|
/*
|
|
* 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 and signal need_resched()
|
|
* contention.
|
|
*/
|
|
if ((zone_contended == COMPACT_CONTENDED_SCHED)
|
|
|| fatal_signal_pending(current)) {
|
|
*contended = COMPACT_CONTENDED_SCHED;
|
|
goto break_loop;
|
|
}
|
|
|
|
continue;
|
|
break_loop:
|
|
/*
|
|
* We might not have tried all the zones, so be conservative
|
|
* and assume they are not all lock contended.
|
|
*/
|
|
all_zones_contended = 0;
|
|
break;
|
|
}
|
|
|
|
/*
|
|
* If at least one zone wasn't deferred or skipped, we report if all
|
|
* zones that were tried were lock contended.
|
|
*/
|
|
if (rc > COMPACT_SKIPPED && all_zones_contended)
|
|
*contended = COMPACT_CONTENDED_LOCK;
|
|
|
|
return rc;
|
|
}
|
|
|
|
|
|
/* Compact all zones within a node */
|
|
static void __compact_pgdat(pg_data_t *pgdat, struct compact_control *cc)
|
|
{
|
|
int zoneid;
|
|
struct zone *zone;
|
|
|
|
for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
|
|
|
|
zone = &pgdat->node_zones[zoneid];
|
|
if (!populated_zone(zone))
|
|
continue;
|
|
|
|
cc->nr_freepages = 0;
|
|
cc->nr_migratepages = 0;
|
|
cc->zone = zone;
|
|
INIT_LIST_HEAD(&cc->freepages);
|
|
INIT_LIST_HEAD(&cc->migratepages);
|
|
|
|
/*
|
|
* When called via /proc/sys/vm/compact_memory
|
|
* this makes sure we compact the whole zone regardless of
|
|
* cached scanner positions.
|
|
*/
|
|
if (is_via_compact_memory(cc->order))
|
|
__reset_isolation_suitable(zone);
|
|
|
|
if (is_via_compact_memory(cc->order) ||
|
|
!compaction_deferred(zone, cc->order))
|
|
compact_zone(zone, cc);
|
|
|
|
VM_BUG_ON(!list_empty(&cc->freepages));
|
|
VM_BUG_ON(!list_empty(&cc->migratepages));
|
|
|
|
if (is_via_compact_memory(cc->order))
|
|
continue;
|
|
|
|
if (zone_watermark_ok(zone, cc->order,
|
|
low_wmark_pages(zone), 0, 0))
|
|
compaction_defer_reset(zone, cc->order, false);
|
|
}
|
|
}
|
|
|
|
void compact_pgdat(pg_data_t *pgdat, int order)
|
|
{
|
|
struct compact_control cc = {
|
|
.order = order,
|
|
.mode = MIGRATE_ASYNC,
|
|
};
|
|
|
|
if (!order)
|
|
return;
|
|
|
|
__compact_pgdat(pgdat, &cc);
|
|
}
|
|
|
|
static void compact_node(int nid)
|
|
{
|
|
struct compact_control cc = {
|
|
.order = -1,
|
|
.mode = MIGRATE_SYNC,
|
|
.ignore_skip_hint = true,
|
|
};
|
|
|
|
__compact_pgdat(NODE_DATA(nid), &cc);
|
|
}
|
|
|
|
/* 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);
|
|
}
|
|
|
|
/* The written value is actually unused, all memory is compacted */
|
|
int sysctl_compact_memory;
|
|
|
|
/*
|
|
* 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 __user *buffer, size_t *length, loff_t *ppos)
|
|
{
|
|
if (write)
|
|
compact_nodes();
|
|
|
|
return 0;
|
|
}
|
|
|
|
int sysctl_extfrag_handler(struct ctl_table *table, int write,
|
|
void __user *buffer, size_t *length, loff_t *ppos)
|
|
{
|
|
proc_dointvec_minmax(table, write, buffer, length, ppos);
|
|
|
|
return 0;
|
|
}
|
|
|
|
#if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
|
|
static ssize_t sysfs_compact_node(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(compact, S_IWUSR, NULL, sysfs_compact_node);
|
|
|
|
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 */
|
|
|
|
#endif /* CONFIG_COMPACTION */
|