The patch titled Subject: mm/compaction: add support for >0 order folio memory compaction has been added to the -mm mm-unstable branch. Its filename is mm-compaction-add-support-for-0-order-folio-memory-compaction.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-compaction-add-support-for-0-order-folio-memory-compaction.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Zi Yan <ziy@xxxxxxxxxx> Subject: mm/compaction: add support for >0 order folio memory compaction Date: Fri, 16 Feb 2024 12:04:31 -0500 Before last commit, memory compaction only migrates order-0 folios and skips >0 order folios. Last commit splits all >0 order folios during compaction. This commit migrates >0 order folios during compaction by keeping isolated free pages at their original size without splitting them into order-0 pages and using them directly during migration process. What is different from the prior implementation: 1. All isolated free pages are kept in a NR_PAGE_ORDERS array of page lists, where each page list stores free pages in the same order. 2. All free pages are not post_alloc_hook() processed nor buddy pages, although their orders are stored in first page's private like buddy pages. 3. During migration, in new page allocation time (i.e., in compaction_alloc()), free pages are then processed by post_alloc_hook(). When migration fails and a new page is returned (i.e., in compaction_free()), free pages are restored by reversing the post_alloc_hook() operations using newly added free_pages_prepare_fpi_none(). Step 3 is done for a latter optimization that splitting and/or merging free pages during compaction becomes easier. Note: without splitting free pages, compaction can end prematurely due to migration will return -ENOMEM even if there is free pages. This happens when no order-0 free page exist and compaction_alloc() return NULL. Link: https://lkml.kernel.org/r/20240216170432.1268753-4-zi.yan@xxxxxxxx Signed-off-by: Zi Yan <ziy@xxxxxxxxxx> Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx> Tested-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> Tested-by: Yu Zhao <yuzhao@xxxxxxxxxx> Cc: Adam Manzanares <a.manzanares@xxxxxxxxxxx> Cc: David Hildenbrand <david@xxxxxxxxxx> Cc: Huang Ying <ying.huang@xxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx> Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Luis Chamberlain <mcgrof@xxxxxxxxxx> Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> Cc: Ryan Roberts <ryan.roberts@xxxxxxx> Cc: Vishal Moola (Oracle) <vishal.moola@xxxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Cc: Yin Fengwei <fengwei.yin@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/compaction.c | 140 +++++++++++++++++++++++++--------------------- mm/internal.h | 4 - mm/page_alloc.c | 2 3 files changed, 83 insertions(+), 63 deletions(-) --- a/mm/compaction.c~mm-compaction-add-support-for-0-order-folio-memory-compaction +++ a/mm/compaction.c @@ -66,45 +66,56 @@ static inline void count_compact_events( #define COMPACTION_HPAGE_ORDER (PMD_SHIFT - PAGE_SHIFT) #endif -static unsigned long release_freepages(struct list_head *freelist) +static void split_map_pages(struct list_head *freepages) { + unsigned int i, order; struct page *page, *next; - unsigned long high_pfn = 0; + LIST_HEAD(tmp_list); - 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; - } + for (order = 0; order < NR_PAGE_ORDERS; order++) { + list_for_each_entry_safe(page, next, &freepages[order], lru) { + unsigned int nr_pages; - return high_pfn; + list_del(&page->lru); + + nr_pages = 1 << order; + + post_alloc_hook(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 void split_map_pages(struct list_head *list) +static unsigned long release_free_list(struct list_head *freepages) { - unsigned int i, order, nr_pages; - struct page *page, *next; - LIST_HEAD(tmp_list); - - list_for_each_entry_safe(page, next, list, lru) { - list_del(&page->lru); + int order; + unsigned long high_pfn = 0; - order = page_private(page); - nr_pages = 1 << order; + for (order = 0; order < NR_PAGE_ORDERS; order++) { + struct page *page, *next; - post_alloc_hook(page, order, __GFP_MOVABLE); - if (order) - split_page(page, order); + list_for_each_entry_safe(page, next, &freepages[order], lru) { + unsigned long pfn = page_to_pfn(page); - for (i = 0; i < nr_pages; i++) { - list_add(&page->lru, &tmp_list); - page++; + list_del(&page->lru); + /* + * Convert free pages into post allocation pages, so + * that we can free them via __free_page. + */ + post_alloc_hook(page, order, __GFP_MOVABLE); + __free_pages(page, order); + if (pfn > high_pfn) + high_pfn = pfn; } } - - list_splice(&tmp_list, list); + return high_pfn; } #ifdef CONFIG_COMPACTION @@ -657,7 +668,7 @@ static unsigned long isolate_freepages_b nr_scanned += isolated - 1; total_isolated += isolated; cc->nr_freepages += isolated; - list_add_tail(&page->lru, freelist); + list_add_tail(&page->lru, &freelist[order]); if (!strict && cc->nr_migratepages <= cc->nr_freepages) { blockpfn += isolated; @@ -722,7 +733,11 @@ isolate_freepages_range(struct compact_c unsigned long start_pfn, unsigned long end_pfn) { unsigned long isolated, pfn, block_start_pfn, block_end_pfn; - LIST_HEAD(freelist); + int order; + struct list_head tmp_freepages[NR_PAGE_ORDERS]; + + for (order = 0; order < NR_PAGE_ORDERS; order++) + INIT_LIST_HEAD(&tmp_freepages[order]); pfn = start_pfn; block_start_pfn = pageblock_start_pfn(pfn); @@ -753,7 +768,7 @@ isolate_freepages_range(struct compact_c break; isolated = isolate_freepages_block(cc, &isolate_start_pfn, - block_end_pfn, &freelist, 0, true); + block_end_pfn, tmp_freepages, 0, true); /* * In strict mode, isolate_freepages_block() returns 0 if @@ -770,15 +785,15 @@ isolate_freepages_range(struct compact_c */ } - /* __isolate_free_page() does not map the pages */ - split_map_pages(&freelist); - if (pfn < end_pfn) { /* Loop terminated early, cleanup. */ - release_freepages(&freelist); + release_free_list(tmp_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; } @@ -1494,7 +1509,7 @@ fast_isolate_around(struct compact_contr if (!page) return; - isolate_freepages_block(cc, &start_pfn, end_pfn, &cc->freepages, 1, false); + 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 (start_pfn == end_pfn && !cc->no_set_skip_hint) @@ -1623,7 +1638,7 @@ static void fast_isolate_freepages(struc nr_scanned += nr_isolated - 1; total_isolated += nr_isolated; cc->nr_freepages += nr_isolated; - list_add_tail(&page->lru, &cc->freepages); + list_add_tail(&page->lru, &cc->freepages[order]); count_compact_events(COMPACTISOLATED, nr_isolated); } else { /* If isolation fails, abort the search */ @@ -1700,13 +1715,12 @@ static void isolate_freepages(struct com 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 */ fast_isolate_freepages(cc); if (cc->nr_freepages) - goto splitmap; + return; /* * Initialise the free scanner. The starting point is where we last @@ -1766,7 +1780,7 @@ static void isolate_freepages(struct com /* Found a block suitable for isolating free pages from. */ nr_isolated = isolate_freepages_block(cc, &isolate_start_pfn, - block_end_pfn, freelist, stride, false); + block_end_pfn, cc->freepages, stride, false); /* Update the skip hint if the full pageblock was scanned */ if (isolate_start_pfn == block_end_pfn) @@ -1807,10 +1821,6 @@ static void isolate_freepages(struct com * 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); } /* @@ -1821,24 +1831,22 @@ static struct folio *compaction_alloc(st { struct compact_control *cc = (struct compact_control *)data; struct folio *dst; + int order = folio_order(src); - /* this makes migrate_pages() split the source page and retry */ - if (folio_test_large(src) > 0) - return NULL; - - if (list_empty(&cc->freepages)) { + if (list_empty(&cc->freepages[order])) { isolate_freepages(cc); - - if (list_empty(&cc->freepages)) + if (list_empty(&cc->freepages[order])) return NULL; } - dst = list_entry(cc->freepages.next, struct folio, lru); + dst = list_first_entry(&cc->freepages[order], struct folio, lru); list_del(&dst->lru); - cc->nr_freepages--; - cc->nr_migratepages -= 1 << folio_order(src); - - return dst; + post_alloc_hook(&dst->page, order, __GFP_MOVABLE); + if (order) + prep_compound_page(&dst->page, order); + cc->nr_freepages -= 1 << order; + cc->nr_migratepages -= 1 << order; + return page_rmappable_folio(&dst->page); } /* @@ -1849,10 +1857,19 @@ static struct folio *compaction_alloc(st static void compaction_free(struct folio *dst, unsigned long data) { struct compact_control *cc = (struct compact_control *)data; + int order = folio_order(dst); + struct page *page = &dst->page; - list_add(&dst->lru, &cc->freepages); - cc->nr_freepages++; - cc->nr_migratepages += 1 << folio_order(dst); + if (folio_put_testzero(dst)) { + free_pages_prepare(page, order); + list_add(&dst->lru, &cc->freepages[order]); + cc->nr_freepages += 1 << order; + } + cc->nr_migratepages += 1 << order; + /* + * someone else has referenced the page, we cannot take it back to our + * free list. + */ } /* possible outcome of isolate_migratepages */ @@ -2476,6 +2493,7 @@ compact_zone(struct compact_control *cc, const bool sync = cc->mode != MIGRATE_ASYNC; bool update_cached; unsigned int nr_succeeded = 0; + int order; /* * These counters track activities during zone compaction. Initialize @@ -2485,7 +2503,8 @@ compact_zone(struct compact_control *cc, cc->total_free_scanned = 0; cc->nr_migratepages = 0; cc->nr_freepages = 0; - INIT_LIST_HEAD(&cc->freepages); + for (order = 0; order < NR_PAGE_ORDERS; order++) + INIT_LIST_HEAD(&cc->freepages[order]); INIT_LIST_HEAD(&cc->migratepages); cc->migratetype = gfp_migratetype(cc->gfp_mask); @@ -2671,7 +2690,7 @@ out: * 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); + unsigned long free_pfn = release_free_list(cc->freepages); cc->nr_freepages = 0; VM_BUG_ON(free_pfn == 0); @@ -2690,7 +2709,6 @@ out: trace_mm_compaction_end(cc, start_pfn, end_pfn, sync, ret); - VM_BUG_ON(!list_empty(&cc->freepages)); VM_BUG_ON(!list_empty(&cc->migratepages)); return ret; --- a/mm/internal.h~mm-compaction-add-support-for-0-order-folio-memory-compaction +++ a/mm/internal.h @@ -447,6 +447,8 @@ extern void prep_compound_page(struct pa extern void post_alloc_hook(struct page *page, unsigned int order, gfp_t gfp_flags); +extern bool free_pages_prepare(struct page *page, unsigned int order); + extern int user_min_free_kbytes; extern void free_unref_page(struct page *page, unsigned int order); @@ -481,7 +483,7 @@ int split_free_page(struct page *free_pa * completes when free_pfn <= migrate_pfn */ struct compact_control { - struct list_head freepages; /* List of free pages to migrate to */ + struct list_head freepages[NR_PAGE_ORDERS]; /* List of free pages to migrate to */ struct list_head migratepages; /* List of pages being migrated */ unsigned int nr_freepages; /* Number of isolated free pages */ unsigned int nr_migratepages; /* Number of pages to migrate */ --- a/mm/page_alloc.c~mm-compaction-add-support-for-0-order-folio-memory-compaction +++ a/mm/page_alloc.c @@ -1080,7 +1080,7 @@ static void kernel_init_pages(struct pag kasan_enable_current(); } -static __always_inline bool free_pages_prepare(struct page *page, +__always_inline bool free_pages_prepare(struct page *page, unsigned int order) { int bad = 0; _ Patches currently in -mm which might be from ziy@xxxxxxxxxx are mm-page_alloc-remove-unused-fpi_flags-in-free_pages_prepare.patch mm-compaction-enable-compacting-0-order-folios.patch mm-compaction-add-support-for-0-order-folio-memory-compaction.patch mm-compaction-optimize-0-order-folio-compaction-with-free-page-split.patch