From c060f943d0929f3e429c5d9522290584f6281d6e Mon Sep 17 00:00:00 2001 From: Laura Abbott Date: Fri, 11 Jan 2013 14:31:51 -0800 Subject: mm: use aligned zone start for pfn_to_bitidx calculation The current calculation in pfn_to_bitidx assumes that (pfn - zone->zone_start_pfn) >> pageblock_order will return the same bit for all pfn in a pageblock. If zone_start_pfn is not aligned to pageblock_nr_pages, this may not always be correct. Consider the following with pageblock order = 10, zone start 2MB: pfn | pfn - zone start | (pfn - zone start) >> page block order ---------------------------------------------------------------- 0x26000 | 0x25e00 | 0x97 0x26100 | 0x25f00 | 0x97 0x26200 | 0x26000 | 0x98 0x26300 | 0x26100 | 0x98 This means that calling {get,set}_pageblock_migratetype on a single page will not set the migratetype for the full block. Fix this by rounding down zone_start_pfn when doing the bitidx calculation. For our use case, the effects of this bug were mostly tied to the fact that CMA allocations would either take a long time or fail to happen. Depending on the driver using CMA, this could result in anything from visual glitches to application failures. Signed-off-by: Laura Abbott Acked-by: Mel Gorman Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/page_alloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'mm/page_alloc.c') diff --git a/mm/page_alloc.c b/mm/page_alloc.c index bc6cc0e913bd..c957805a7f0e 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -5604,7 +5604,7 @@ static inline int pfn_to_bitidx(struct zone *zone, unsigned long pfn) pfn &= (PAGES_PER_SECTION-1); return (pfn >> pageblock_order) * NR_PAGEBLOCK_BITS; #else - pfn = pfn - zone->zone_start_pfn; + pfn = pfn - round_down(zone->zone_start_pfn, pageblock_nr_pages); return (pfn >> pageblock_order) * NR_PAGEBLOCK_BITS; #endif /* CONFIG_SPARSEMEM */ } -- cgit v1.2.3 From 8fb74b9fb2b182d54beee592350d9ea1f325917a Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Fri, 11 Jan 2013 14:32:16 -0800 Subject: mm: compaction: partially revert capture of suitable high-order page Eric Wong reported on 3.7 and 3.8-rc2 that ppoll() got stuck when waiting for POLLIN on a local TCP socket. It was easier to trigger if there was disk IO and dirty pages at the same time and he bisected it to commit 1fb3f8ca0e92 ("mm: compaction: capture a suitable high-order page immediately when it is made available"). The intention of that patch was to improve high-order allocations under memory pressure after changes made to reclaim in 3.6 drastically hurt THP allocations but the approach was flawed. For Eric, the problem was that page->pfmemalloc was not being cleared for captured pages leading to a poor interaction with swap-over-NFS support causing the packets to be dropped. However, I identified a few more problems with the patch including the fact that it can increase contention on zone->lock in some cases which could result in async direct compaction being aborted early. In retrospect the capture patch took the wrong approach. What it should have done is mark the pageblock being migrated as MIGRATE_ISOLATE if it was allocating for THP and avoided races that way. While the patch was showing to improve allocation success rates at the time, the benefit is marginal given the relative complexity and it should be revisited from scratch in the context of the other reclaim-related changes that have taken place since the patch was first written and tested. This patch partially reverts commit 1fb3f8ca0e92 ("mm: compaction: capture a suitable high-order page immediately when it is made available"). Reported-and-tested-by: Eric Wong Tested-by: Eric Dumazet Cc: Signed-off-by: Mel Gorman Cc: David Miller Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/compaction.h | 4 +- include/linux/mm.h | 1 - mm/compaction.c | 92 +++++++--------------------------------------- mm/internal.h | 1 - mm/page_alloc.c | 35 ++++-------------- 5 files changed, 23 insertions(+), 110 deletions(-) (limited to 'mm/page_alloc.c') diff --git a/include/linux/compaction.h b/include/linux/compaction.h index 6ecb6dc2f303..cc7bddeaf553 100644 --- a/include/linux/compaction.h +++ b/include/linux/compaction.h @@ -22,7 +22,7 @@ extern int sysctl_extfrag_handler(struct ctl_table *table, int write, extern int fragmentation_index(struct zone *zone, unsigned int order); extern unsigned long try_to_compact_pages(struct zonelist *zonelist, int order, gfp_t gfp_mask, nodemask_t *mask, - bool sync, bool *contended, struct page **page); + bool sync, bool *contended); extern int compact_pgdat(pg_data_t *pgdat, int order); extern void reset_isolation_suitable(pg_data_t *pgdat); extern unsigned long compaction_suitable(struct zone *zone, int order); @@ -75,7 +75,7 @@ static inline bool compaction_restarting(struct zone *zone, int order) #else static inline unsigned long try_to_compact_pages(struct zonelist *zonelist, int order, gfp_t gfp_mask, nodemask_t *nodemask, - bool sync, bool *contended, struct page **page) + bool sync, bool *contended) { return COMPACT_CONTINUE; } diff --git a/include/linux/mm.h b/include/linux/mm.h index 63204078f72b..66e2f7c61e5c 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -455,7 +455,6 @@ void put_pages_list(struct list_head *pages); void split_page(struct page *page, unsigned int order); int split_free_page(struct page *page); -int capture_free_page(struct page *page, int alloc_order, int migratetype); /* * Compound pages have a destructor function. Provide a diff --git a/mm/compaction.c b/mm/compaction.c index f8f5c111b7d7..c62bd063d766 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -816,6 +816,7 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone, static int compact_finished(struct zone *zone, struct compact_control *cc) { + unsigned int order; unsigned long watermark; if (fatal_signal_pending(current)) @@ -850,22 +851,16 @@ static int compact_finished(struct zone *zone, return COMPACT_CONTINUE; /* Direct compactor: Is a suitable page free? */ - if (cc->page) { - /* Was a suitable page captured? */ - if (*cc->page) + for (order = cc->order; order < MAX_ORDER; order++) { + struct free_area *area = &zone->free_area[order]; + + /* Job done if page is free of the right migratetype */ + if (!list_empty(&area->free_list[cc->migratetype])) + return COMPACT_PARTIAL; + + /* Job done if allocation would set block type */ + if (cc->order >= pageblock_order && area->nr_free) return COMPACT_PARTIAL; - } else { - unsigned int order; - for (order = cc->order; order < MAX_ORDER; order++) { - struct free_area *area = &zone->free_area[cc->order]; - /* Job done if page is free of the right migratetype */ - if (!list_empty(&area->free_list[cc->migratetype])) - return COMPACT_PARTIAL; - - /* Job done if allocation would set block type */ - if (cc->order >= pageblock_order && area->nr_free) - return COMPACT_PARTIAL; - } } return COMPACT_CONTINUE; @@ -921,60 +916,6 @@ unsigned long compaction_suitable(struct zone *zone, int order) return COMPACT_CONTINUE; } -static void compact_capture_page(struct compact_control *cc) -{ - unsigned long flags; - int mtype, mtype_low, mtype_high; - - if (!cc->page || *cc->page) - return; - - /* - * For MIGRATE_MOVABLE allocations we capture a suitable page ASAP - * regardless of the migratetype of the freelist is is captured from. - * This is fine because the order for a high-order MIGRATE_MOVABLE - * allocation is typically at least a pageblock size and overall - * fragmentation is not impaired. Other allocation types must - * capture pages from their own migratelist because otherwise they - * could pollute other pageblocks like MIGRATE_MOVABLE with - * difficult to move pages and making fragmentation worse overall. - */ - if (cc->migratetype == MIGRATE_MOVABLE) { - mtype_low = 0; - mtype_high = MIGRATE_PCPTYPES; - } else { - mtype_low = cc->migratetype; - mtype_high = cc->migratetype + 1; - } - - /* Speculatively examine the free lists without zone lock */ - for (mtype = mtype_low; mtype < mtype_high; mtype++) { - int order; - for (order = cc->order; order < MAX_ORDER; order++) { - struct page *page; - struct free_area *area; - area = &(cc->zone->free_area[order]); - if (list_empty(&area->free_list[mtype])) - continue; - - /* Take the lock and attempt capture of the page */ - if (!compact_trylock_irqsave(&cc->zone->lock, &flags, cc)) - return; - if (!list_empty(&area->free_list[mtype])) { - page = list_entry(area->free_list[mtype].next, - struct page, lru); - if (capture_free_page(page, cc->order, mtype)) { - spin_unlock_irqrestore(&cc->zone->lock, - flags); - *cc->page = page; - return; - } - } - spin_unlock_irqrestore(&cc->zone->lock, flags); - } - } -} - static int compact_zone(struct zone *zone, struct compact_control *cc) { int ret; @@ -1054,9 +995,6 @@ static int compact_zone(struct zone *zone, struct compact_control *cc) goto out; } } - - /* Capture a page now if it is a suitable size */ - compact_capture_page(cc); } out: @@ -1069,8 +1007,7 @@ out: static unsigned long compact_zone_order(struct zone *zone, int order, gfp_t gfp_mask, - bool sync, bool *contended, - struct page **page) + bool sync, bool *contended) { unsigned long ret; struct compact_control cc = { @@ -1080,7 +1017,6 @@ static unsigned long compact_zone_order(struct zone *zone, .migratetype = allocflags_to_migratetype(gfp_mask), .zone = zone, .sync = sync, - .page = page, }; INIT_LIST_HEAD(&cc.freepages); INIT_LIST_HEAD(&cc.migratepages); @@ -1110,7 +1046,7 @@ int sysctl_extfrag_threshold = 500; */ unsigned long try_to_compact_pages(struct zonelist *zonelist, int order, gfp_t gfp_mask, nodemask_t *nodemask, - bool sync, bool *contended, struct page **page) + bool sync, bool *contended) { enum zone_type high_zoneidx = gfp_zone(gfp_mask); int may_enter_fs = gfp_mask & __GFP_FS; @@ -1136,7 +1072,7 @@ unsigned long try_to_compact_pages(struct zonelist *zonelist, int status; status = compact_zone_order(zone, order, gfp_mask, sync, - contended, page); + contended); rc = max(status, rc); /* If a normal allocation would succeed, stop compacting */ @@ -1192,7 +1128,6 @@ int compact_pgdat(pg_data_t *pgdat, int order) struct compact_control cc = { .order = order, .sync = false, - .page = NULL, }; return __compact_pgdat(pgdat, &cc); @@ -1203,7 +1138,6 @@ static int compact_node(int nid) struct compact_control cc = { .order = -1, .sync = true, - .page = NULL, }; return __compact_pgdat(NODE_DATA(nid), &cc); diff --git a/mm/internal.h b/mm/internal.h index d597f94cc205..9ba21100ebf3 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -135,7 +135,6 @@ struct compact_control { int migratetype; /* MOVABLE, RECLAIMABLE etc */ struct zone *zone; bool contended; /* True if a lock was contended */ - struct page **page; /* Page captured of requested size */ }; unsigned long diff --git a/mm/page_alloc.c b/mm/page_alloc.c index c957805a7f0e..df2022ff0c8a 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1384,14 +1384,8 @@ void split_page(struct page *page, unsigned int order) set_page_refcounted(page + i); } -/* - * Similar to the split_page family of functions except that the page - * required at the given order and being isolated now to prevent races - * with parallel allocators - */ -int capture_free_page(struct page *page, int alloc_order, int migratetype) +static int __isolate_free_page(struct page *page, unsigned int order) { - unsigned int order; unsigned long watermark; struct zone *zone; int mt; @@ -1399,7 +1393,6 @@ int capture_free_page(struct page *page, int alloc_order, int migratetype) BUG_ON(!PageBuddy(page)); zone = page_zone(page); - order = page_order(page); mt = get_pageblock_migratetype(page); if (mt != MIGRATE_ISOLATE) { @@ -1408,7 +1401,7 @@ int capture_free_page(struct page *page, int alloc_order, int migratetype) if (!zone_watermark_ok(zone, 0, watermark, 0, 0)) return 0; - __mod_zone_freepage_state(zone, -(1UL << alloc_order), mt); + __mod_zone_freepage_state(zone, -(1UL << order), mt); } /* Remove page from free list */ @@ -1416,11 +1409,7 @@ int capture_free_page(struct page *page, int alloc_order, int migratetype) zone->free_area[order].nr_free--; rmv_page_order(page); - if (alloc_order != order) - expand(zone, page, alloc_order, order, - &zone->free_area[order], migratetype); - - /* Set the pageblock if the captured page is at least a pageblock */ + /* Set the pageblock if the isolated page is at least a pageblock */ if (order >= pageblock_order - 1) { struct page *endpage = page + (1 << order) - 1; for (; page < endpage; page += pageblock_nr_pages) { @@ -1431,7 +1420,7 @@ int capture_free_page(struct page *page, int alloc_order, int migratetype) } } - return 1UL << alloc_order; + return 1UL << order; } /* @@ -1449,10 +1438,9 @@ int split_free_page(struct page *page) unsigned int order; int nr_pages; - BUG_ON(!PageBuddy(page)); order = page_order(page); - nr_pages = capture_free_page(page, order, 0); + nr_pages = __isolate_free_page(page, order); if (!nr_pages) return 0; @@ -2136,8 +2124,6 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order, bool *contended_compaction, bool *deferred_compaction, unsigned long *did_some_progress) { - struct page *page = NULL; - if (!order) return NULL; @@ -2149,16 +2135,12 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order, current->flags |= PF_MEMALLOC; *did_some_progress = try_to_compact_pages(zonelist, order, gfp_mask, nodemask, sync_migration, - contended_compaction, &page); + contended_compaction); current->flags &= ~PF_MEMALLOC; - /* If compaction captured a page, prep and use it */ - if (page) { - prep_new_page(page, order, gfp_mask); - goto got_page; - } - if (*did_some_progress != COMPACT_SKIPPED) { + struct page *page; + /* Page migration frees to the PCP lists but we want merging */ drain_pages(get_cpu()); put_cpu(); @@ -2168,7 +2150,6 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order, alloc_flags & ~ALLOC_NO_WATERMARKS, preferred_zone, migratetype); if (page) { -got_page: preferred_zone->compact_blockskip_flush = false; preferred_zone->compact_considered = 0; preferred_zone->compact_defer_shift = 0; -- cgit v1.2.3