From 753341a4b85ff337487b9959c71c529f522004f4 Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Mon, 8 Oct 2012 16:32:40 -0700 Subject: revert "mm: have order > 0 compaction start off where it left" This reverts commit 7db8889ab05b ("mm: have order > 0 compaction start off where it left") and commit de74f1cc ("mm: have order > 0 compaction start near a pageblock with free pages"). These patches were a good idea and tests confirmed that they massively reduced the amount of scanning but the implementation is complex and tricky to understand. A later patch will cache what pageblocks should be skipped and reimplements the concept of compact_cached_free_pfn on top for both migration and free scanners. Signed-off-by: Mel Gorman Acked-by: Rik van Riel Cc: Richard Davies Cc: Shaohua Li Cc: Avi Kivity Acked-by: Rafael Aquini Acked-by: Minchan Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/compaction.c | 65 +++++---------------------------------------------------- 1 file changed, 5 insertions(+), 60 deletions(-) (limited to 'mm/compaction.c') diff --git a/mm/compaction.c b/mm/compaction.c index bdf6e13045ea..db76361a3117 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -537,20 +537,6 @@ next_pageblock: #endif /* CONFIG_COMPACTION || CONFIG_CMA */ #ifdef CONFIG_COMPACTION -/* - * Returns the start pfn of the last 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; -} - /* * Based on information in the current compact_control, find blocks * suitable for isolating free pages from and then isolate them. @@ -619,19 +605,8 @@ 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 the free scanner has wrapped, update - * compact_cached_free_pfn to point to the highest - * pageblock with free pages. This reduces excessive - * scanning of full pageblocks near the end of the - * zone - */ - if (cc->order > 0 && cc->wrapped) - zone->compact_cached_free_pfn = high_pfn; - } } /* split_free_page does not map the pages */ @@ -639,11 +614,6 @@ static void isolate_freepages(struct zone *zone, cc->free_pfn = high_pfn; cc->nr_freepages = nr_freepages; - - /* If compact_cached_free_pfn is reset then set it now */ - if (cc->order > 0 && !cc->wrapped && - zone->compact_cached_free_pfn == start_free_pfn(zone)) - zone->compact_cached_free_pfn = high_pfn; } /* @@ -738,26 +708,8 @@ static int compact_finished(struct zone *zone, if (fatal_signal_pending(current)) return COMPACT_PARTIAL; - /* - * A full (order == -1) compaction run starts at the beginning and - * end of a zone; it completes when the migrate and free scanner meet. - * A partial (order > 0) compaction can start with the free scanner - * at a random point in the zone, and may have to restart. - */ - 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 = start_free_pfn(zone); - zone->compact_cached_free_pfn = free_pfn; - cc->free_pfn = free_pfn; - cc->wrapped = 1; - return COMPACT_CONTINUE; - } - return COMPACT_COMPLETE; - } - - /* We wrapped around and ended up where we started. */ - if (cc->wrapped && cc->free_pfn <= cc->start_free_pfn) + /* Compaction run completes if the migrate and free scanner meet */ + if (cc->free_pfn <= cc->migrate_pfn) return COMPACT_COMPLETE; /* @@ -863,15 +815,8 @@ static int compact_zone(struct zone *zone, struct compact_control *cc) /* Setup to move all movable pages to the end of the zone */ cc->migrate_pfn = zone->zone_start_pfn; - - if (cc->order > 0) { - /* Incremental compaction. Start where the last one stopped. */ - cc->free_pfn = zone->compact_cached_free_pfn; - cc->start_free_pfn = cc->free_pfn; - } else { - /* Order == -1 starts at the end of the zone. */ - cc->free_pfn = start_free_pfn(zone); - } + cc->free_pfn = cc->migrate_pfn + zone->spanned_pages; + cc->free_pfn &= ~(pageblock_nr_pages-1); migrate_prep_local(); -- cgit v1.2.3-55-g7522