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mm/contig_alloc: support __GFP_COMP

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Patch series "mm/hugetlb: alloc/free gigantic folios", v2.

Use __GFP_COMP for gigantic folios can greatly reduce not only the amount
of code but also the allocation and free time.

Approximate LOC to mm/hugetlb.c: +60, -240

Allocate and free 500 1GB hugeTLB memory without HVO by:
  time echo 500 >/sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages
  time echo 0 >/sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages

       Before  After
Alloc  ~13s    ~10s
Free   ~15s    <1s

The above magnitude generally holds for multiple x86 and arm64 CPU
models.

Perf profile before:
  Alloc
    - 99.99% alloc_pool_huge_folio
       - __alloc_fresh_hugetlb_folio
          - 83.23% alloc_contig_pages_noprof
             - 47.46% alloc_contig_range_noprof
                - 20.96% isolate_freepages_range
                     16.10% split_page
                - 14.10% start_isolate_page_range
                - 12.02% undo_isolate_page_range

  Free
    - update_and_free_pages_bulk
       - 87.71% free_contig_range
          - 76.02% free_unref_page
             - 41.30% free_unref_page_commit
                - 32.58% free_pcppages_bulk
                   - 24.75% __free_one_page
               13.96% _raw_spin_trylock
         12.27% __update_and_free_hugetlb_folio

Perf profile after:
  Alloc
    - 99.99% alloc_pool_huge_folio
         alloc_gigantic_folio
       - alloc_contig_pages_noprof
          - 59.15% alloc_contig_range_noprof
             - 20.72% start_isolate_page_range
               20.64% prep_new_page
             - 17.13% undo_isolate_page_range

  Free
    - update_and_free_pages_bulk
       - __folio_put
       - __free_pages_ok
            7.46% free_tail_page_prepare
          - 1.97% free_one_page
               1.86% __free_one_page

This patch (of 3):

Support __GFP_COMP in alloc_contig_range().  When the flag is set, upon
success the function returns a large folio prepared by prep_new_page(),
rather than a range of order-0 pages prepared by split_free_pages() (which
is renamed from split_map_pages()).

alloc_contig_range() can be used to allocate folios larger than
MAX_PAGE_ORDER, e.g., gigantic hugeTLB folios.  So on the free path,
free_one_page() needs to handle that by split_large_buddy().

[akpm@linux-foundation.org: fix folio_alloc_gigantic_noprof() WARN expression, per Yu Liao]
Link: https://lkml.kernel.org/r/20240814035451.773331-1-yuzhao@google.com
Link: https://lkml.kernel.org/r/20240814035451.773331-2-yuzhao@google.com
Signed-off-by: Yu Zhao <yuzhao@google.com>
Acked-by: Zi Yan <ziy@nvidia.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Frank van der Linden <fvdl@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Yu Zhao 2024-08-13 21:54:49 -06:00 committed by Andrew Morton
parent f77f0c7514
commit e98337d11b
3 changed files with 108 additions and 67 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
include/linux/gfp.h
View File

@ -446,4 +446,27 @@ extern struct page *alloc_contig_pages_noprof(unsigned long nr_pages, gfp_t gfp_
#endif
void free_contig_range(unsigned long pfn, unsigned long nr_pages);
#ifdef CONFIG_CONTIG_ALLOC
static inline struct folio *folio_alloc_gigantic_noprof(int order, gfp_t gfp,
int nid, nodemask_t *node)
{
struct page *page;
if (WARN_ON(!order || !(gfp & __GFP_COMP)))
return NULL;
page = alloc_contig_pages_noprof(1 << order, gfp, nid, node);
return page ? page_folio(page) : NULL;
}
#else
static inline struct folio *folio_alloc_gigantic_noprof(int order, gfp_t gfp,
int nid, nodemask_t *node)
{
return NULL;
}
#endif
/* This should be paired with folio_put() rather than free_contig_range(). */
#define folio_alloc_gigantic(...) alloc_hooks(folio_alloc_gigantic_noprof(__VA_ARGS__))
#endif /* __LINUX_GFP_H */

41
mm/compaction.c
View File

@ -86,33 +86,6 @@ static struct page *mark_allocated_noprof(struct page *page, unsigned int order,
}
#define mark_allocated(...) alloc_hooks(mark_allocated_noprof(__VA_ARGS__))
static void split_map_pages(struct list_head *freepages)
{
unsigned int i, order;
struct page *page, *next;
LIST_HEAD(tmp_list);
for (order = 0; order < NR_PAGE_ORDERS; order++) {
list_for_each_entry_safe(page, next, &freepages[order], lru) {
unsigned int nr_pages;
list_del(&page->lru);
nr_pages = 1 << order;
mark_allocated(page, order, __GFP_MOVABLE);
if (order)
split_page(page, order);
for (i = 0; i < nr_pages; i++) {
list_add(&page->lru, &tmp_list);
page++;
}
}
list_splice_init(&tmp_list, &freepages[0]);
}
}
static unsigned long release_free_list(struct list_head *freepages)
{
int order;
@ -742,11 +715,11 @@ isolate_fail:
*
* 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.
* undo its actions and return zero. cc->freepages[] are empty.
*
* 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).
* a free page). cc->freepages[] contain free pages isolated.
*/
unsigned long
isolate_freepages_range(struct compact_control *cc,
@ -754,10 +727,9 @@ isolate_freepages_range(struct compact_control *cc,
{
unsigned long isolated, pfn, block_start_pfn, block_end_pfn;
int order;
struct list_head tmp_freepages[NR_PAGE_ORDERS];
for (order = 0; order < NR_PAGE_ORDERS; order++)
INIT_LIST_HEAD(&tmp_freepages[order]);
INIT_LIST_HEAD(&cc->freepages[order]);
pfn = start_pfn;
block_start_pfn = pageblock_start_pfn(pfn);
@ -788,7 +760,7 @@ isolate_freepages_range(struct compact_control *cc,
break;
isolated = isolate_freepages_block(cc, &isolate_start_pfn,
block_end_pfn, tmp_freepages, 0, true);
block_end_pfn, cc->freepages, 0, true);
/*
* In strict mode, isolate_freepages_block() returns 0 if
@ -807,13 +779,10 @@ isolate_freepages_range(struct compact_control *cc,
if (pfn < end_pfn) {
/* Loop terminated early, cleanup. */
release_free_list(tmp_freepages);
release_free_list(cc->freepages);
return 0;
}
/* __isolate_free_page() does not map the pages */
split_map_pages(tmp_freepages);
/* We don't use freelists for anything. */
return pfn;
}

111
mm/page_alloc.c
View File

@ -1196,16 +1196,36 @@ static void free_pcppages_bulk(struct zone *zone, int count,
spin_unlock_irqrestore(&zone->lock, flags);
}
/* Split a multi-block free page into its individual pageblocks. */
static void split_large_buddy(struct zone *zone, struct page *page,
unsigned long pfn, int order, fpi_t fpi)
{
unsigned long end = pfn + (1 << order);
VM_WARN_ON_ONCE(!IS_ALIGNED(pfn, 1 << order));
/* Caller removed page from freelist, buddy info cleared! */
VM_WARN_ON_ONCE(PageBuddy(page));
if (order > pageblock_order)
order = pageblock_order;
while (pfn != end) {
int mt = get_pfnblock_migratetype(page, pfn);
__free_one_page(page, pfn, zone, order, mt, fpi);
pfn += 1 << order;
page = pfn_to_page(pfn);
}
}
static void free_one_page(struct zone *zone, struct page *page,
unsigned long pfn, unsigned int order,
fpi_t fpi_flags)
{
unsigned long flags;
int migratetype;
spin_lock_irqsave(&zone->lock, flags);
migratetype = get_pfnblock_migratetype(page, pfn);
__free_one_page(page, pfn, zone, order, migratetype, fpi_flags);
split_large_buddy(zone, page, pfn, order, fpi_flags);
spin_unlock_irqrestore(&zone->lock, flags);
}
@ -1697,27 +1717,6 @@ static unsigned long find_large_buddy(unsigned long start_pfn)
return start_pfn;
}
/* Split a multi-block free page into its individual pageblocks */
static void split_large_buddy(struct zone *zone, struct page *page,
unsigned long pfn, int order)
{
unsigned long end_pfn = pfn + (1 << order);
VM_WARN_ON_ONCE(order <= pageblock_order);
VM_WARN_ON_ONCE(pfn & (pageblock_nr_pages - 1));
/* Caller removed page from freelist, buddy info cleared! */
VM_WARN_ON_ONCE(PageBuddy(page));
while (pfn != end_pfn) {
int mt = get_pfnblock_migratetype(page, pfn);
__free_one_page(page, pfn, zone, pageblock_order, mt, FPI_NONE);
pfn += pageblock_nr_pages;
page = pfn_to_page(pfn);
}
}
/**
* move_freepages_block_isolate - move free pages in block for page isolation
* @zone: the zone
@ -1758,7 +1757,7 @@ bool move_freepages_block_isolate(struct zone *zone, struct page *page,
del_page_from_free_list(buddy, zone, order,
get_pfnblock_migratetype(buddy, pfn));
set_pageblock_migratetype(page, migratetype);
split_large_buddy(zone, buddy, pfn, order);
split_large_buddy(zone, buddy, pfn, order, FPI_NONE);
return true;
}
@ -1769,7 +1768,7 @@ bool move_freepages_block_isolate(struct zone *zone, struct page *page,
del_page_from_free_list(page, zone, order,
get_pfnblock_migratetype(page, pfn));
set_pageblock_migratetype(page, migratetype);
split_large_buddy(zone, page, pfn, order);
split_large_buddy(zone, page, pfn, order, FPI_NONE);
return true;
}
move:
@ -6437,6 +6436,31 @@ int __alloc_contig_migrate_range(struct compact_control *cc,
return (ret < 0) ? ret : 0;
}
static void split_free_pages(struct list_head *list)
{
int order;
for (order = 0; order < NR_PAGE_ORDERS; order++) {
struct page *page, *next;
int nr_pages = 1 << order;
list_for_each_entry_safe(page, next, &list[order], lru) {
int i;
post_alloc_hook(page, order, __GFP_MOVABLE);
if (!order)
continue;
split_page(page, order);
/* Add all subpages to the order-0 head, in sequence. */
list_del(&page->lru);
for (i = 0; i < nr_pages; i++)
list_add_tail(&page[i].lru, &list[0]);
}
}
}
/**
* alloc_contig_range() -- tries to allocate given range of pages
* @start: start PFN to allocate
@ -6549,12 +6573,25 @@ int alloc_contig_range_noprof(unsigned long start, unsigned long end,
goto done;
}
/* Free head and tail (if any) */
if (start != outer_start)
free_contig_range(outer_start, start - outer_start);
if (end != outer_end)
free_contig_range(end, outer_end - end);
if (!(gfp_mask & __GFP_COMP)) {
split_free_pages(cc.freepages);
/* Free head and tail (if any) */
if (start != outer_start)
free_contig_range(outer_start, start - outer_start);
if (end != outer_end)
free_contig_range(end, outer_end - end);
} else if (start == outer_start && end == outer_end && is_power_of_2(end - start)) {
struct page *head = pfn_to_page(start);
int order = ilog2(end - start);
check_new_pages(head, order);
prep_new_page(head, order, gfp_mask, 0);
} else {
ret = -EINVAL;
WARN(true, "PFN range: requested [%lu, %lu), allocated [%lu, %lu)\n",
start, end, outer_start, outer_end);
}
done:
undo_isolate_page_range(start, end, migratetype);
return ret;
@ -6663,6 +6700,18 @@ struct page *alloc_contig_pages_noprof(unsigned long nr_pages, gfp_t gfp_mask,
void free_contig_range(unsigned long pfn, unsigned long nr_pages)
{
unsigned long count = 0;
struct folio *folio = pfn_folio(pfn);
if (folio_test_large(folio)) {
int expected = folio_nr_pages(folio);
if (nr_pages == expected)
folio_put(folio);
else
WARN(true, "PFN %lu: nr_pages %lu != expected %d\n",
pfn, nr_pages, expected);
return;
}
for (; nr_pages--; pfn++) {
struct page *page = pfn_to_page(pfn);