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Commit 753341a4 authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds
Browse files

revert "mm: have order > 0 compaction start off where it left" 



This reverts commit 7db8889a ("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: default avatarMel Gorman <mgorman@suse.de>
Acked-by: default avatarRik van Riel <riel@redhat.com>
Cc: Richard Davies <richard@arachsys.com>
Cc: Shaohua Li <shli@kernel.org>
Cc: Avi Kivity <avi@redhat.com>
Acked-by: default avatarRafael Aquini <aquini@redhat.com>
Acked-by: default avatarMinchan Kim <minchan@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f40d1e42

include/linux/mmzone.h

+0 −4
Original line number Diff line number Diff line
@@ -369,10 +369,6 @@ struct zone { 
	 */

	spinlock_t		lock;

	int                     all_unreclaimable; /* All pages pinned */

#if defined CONFIG_COMPACTION || defined CONFIG_CMA

	/* pfn where the last incremental compaction isolated free pages */

	unsigned long		compact_cached_free_pfn;

#endif

#ifdef CONFIG_MEMORY_HOTPLUG

	/* see spanned/present_pages for more description */

	seqlock_t		span_seqlock;

mm/compaction.c

+5 −60
Original line number Diff line number Diff line
@@ -537,20 +537,6 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc, 


#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();

mm/internal.h

+0 −6
Original line number Diff line number Diff line
@@ -118,14 +118,8 @@ struct compact_control { 
	unsigned long nr_freepages;	/* Number of isolated free pages */

	unsigned long nr_migratepages;	/* Number of pages to migrate */

	unsigned long free_pfn;		/* isolate_freepages search base */

	unsigned long start_free_pfn;	/* where we started the search */

	unsigned long migrate_pfn;	/* isolate_migratepages search base */

	bool sync;			/* Synchronous migration */

	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 */

mm/page_alloc.c

+0 −5
Original line number Diff line number Diff line
@@ -4490,11 +4490,6 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat, 


		zone->spanned_pages = size;

		zone->present_pages = realsize;

#if defined CONFIG_COMPACTION || defined CONFIG_CMA

		zone->compact_cached_free_pfn = zone->zone_start_pfn +

						zone->spanned_pages;

		zone->compact_cached_free_pfn &= ~(pageblock_nr_pages-1);

#endif

#ifdef CONFIG_NUMA

		zone->node = nid;

		zone->min_unmapped_pages = (realsize*sysctl_min_unmapped_ratio)