From 09daad2e6ebeb532d789560a14f9a4bce5a8b7b0 Mon Sep 17 00:00:00 2001 From: Rik van Riel Date: Sat, 21 Jul 2012 10:54:13 +1000 Subject: [PATCH] mm: have order > 0 compaction start off where it left This patch makes the comment for cc->wrapped longer, explaining what is really going on. It also incorporates the comment fix pointed out by Minchan. Additionally, Minchan found that, when no pages get isolated, high_pfn could be a value that is much lower than desired, which might potentially cause compaction to skip a range of pages. Only assign zone->compact_cache_free_pfn if we actually isolated free pages for compaction. Split out the calculation to get the start of the last page block in a zone into its own, commented function. Signed-off-by: Rik van Riel Cc: Jim Schutt Acked-by: Minchan Kim Cc: KAMEZAWA Hiroyuki Cc: Mel Gorman Signed-off-by: Andrew Morton --- include/linux/mmzone.h | 2 +- mm/compaction.c | 30 ++++++++++++++++++++++-------- mm/internal.h | 6 +++++- 3 files changed, 28 insertions(+), 10 deletions(-) diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index ffcc32f8ae0d..1aeadce4d56e 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -369,7 +369,7 @@ struct zone { spinlock_t lock; int all_unreclaimable; /* All pages pinned */ #if defined CONFIG_COMPACTION || defined CONFIG_CMA - /* pfn where the last order > 0 compaction isolated free pages */ + /* pfn where the last incremental compaction isolated free pages */ unsigned long compact_cached_free_pfn; #endif #ifdef CONFIG_MEMORY_HOTPLUG diff --git a/mm/compaction.c b/mm/compaction.c index fe990075eeb9..ed851e4d7f84 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -472,10 +472,11 @@ static void isolate_freepages(struct zone *zone, * looking for free pages, the search will restart here as * page migration may have returned some pages to the allocator */ - if (isolated) + if (isolated) { high_pfn = max(high_pfn, pfn); - if (cc->order > 0) - zone->compact_cached_free_pfn = high_pfn; + if (cc->order > 0) + zone->compact_cached_free_pfn = high_pfn; + } } /* split_free_page does not map the pages */ @@ -569,6 +570,21 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone, return ISOLATE_SUCCESS; } +/* + * Returns the start pfn of the laste page block in a zone. + * This is the starting point for full compaction of a zone. + * Compaction searches for free pages from the end of each zone, + * while isolate_freepages_block scans forward inside each page + * block. + */ +static unsigned long start_free_pfn(struct zone *zone) +{ + unsigned long free_pfn; + free_pfn = zone->zone_start_pfn + zone->spanned_pages; + free_pfn &= ~(pageblock_nr_pages-1); + return free_pfn; +} + static int compact_finished(struct zone *zone, struct compact_control *cc) { @@ -587,10 +603,9 @@ static int compact_finished(struct zone *zone, if (cc->free_pfn <= cc->migrate_pfn) { if (cc->order > 0 && !cc->wrapped) { /* We started partway through; restart at the end. */ - unsigned long free_pfn; - free_pfn = zone->zone_start_pfn + zone->spanned_pages; - free_pfn &= ~(pageblock_nr_pages-1); + unsigned long free_pfn = start_free_pfn(zone); zone->compact_cached_free_pfn = free_pfn; + cc->free_pfn = free_pfn; cc->wrapped = 1; return COMPACT_CONTINUE; } @@ -703,8 +718,7 @@ static int compact_zone(struct zone *zone, struct compact_control *cc) cc->start_free_pfn = cc->free_pfn; } else { /* Order == -1 starts at the end of the zone. */ - cc->free_pfn = cc->migrate_pfn + zone->spanned_pages; - cc->free_pfn &= ~(pageblock_nr_pages-1); + cc->free_pfn = start_free_pfn(zone); } migrate_prep_local(); diff --git a/mm/internal.h b/mm/internal.h index 0b724610d207..da6b9b2ed3fc 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -121,7 +121,11 @@ struct compact_control { unsigned long start_free_pfn; /* where we started the search */ unsigned long migrate_pfn; /* isolate_migratepages search base */ bool sync; /* Synchronous migration */ - bool wrapped; /* Last round for order>0 compaction */ + bool wrapped; /* Order > 0 compactions are + incremental, once free_pfn + and migrate_pfn meet, we restart + from the top of the zone; + remember we wrapped around. */ int order; /* order a direct compactor needs */ int migratetype; /* MOVABLE, RECLAIMABLE etc */ -- 2.39.5