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Commit c5d01d0d authored by Michal Hocko's avatar Michal Hocko Committed by Linus Torvalds
Browse files

mm, compaction: simplify __alloc_pages_direct_compact feedback interface 



__alloc_pages_direct_compact communicates potential back off by two
variables:
	- deferred_compaction tells that the compaction returned
	  COMPACT_DEFERRED
	- contended_compaction is set when there is a contention on
	  zone->lock resp. zone->lru_lock locks

__alloc_pages_slowpath then backs of for THP allocation requests to
prevent from long stalls. This is rather messy and it would be much
cleaner to return a single compact result value and hide all the nasty
details into __alloc_pages_direct_compact.

This patch shouldn't introduce any functional changes.

Signed-off-by: default avatarMichal Hocko <mhocko@suse.com>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Acked-by: default avatarHillf Danton <hillf.zj@alibaba-inc.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4f9a358c

mm/page_alloc.c

+31 −36
Original line number Diff line number Diff line
@@ -3185,29 +3185,21 @@ __alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order, 
static struct page *

__alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,

		unsigned int alloc_flags, const struct alloc_context *ac,

		enum migrate_mode mode, int *contended_compaction,

		bool *deferred_compaction)

		enum migrate_mode mode, enum compact_result *compact_result)

{

	enum compact_result compact_result;

	struct page *page;

	int contended_compaction;



	if (!order)

		return NULL;



	current->flags |= PF_MEMALLOC;

	compact_result = try_to_compact_pages(gfp_mask, order, alloc_flags, ac,

						mode, contended_compaction);

	*compact_result = try_to_compact_pages(gfp_mask, order, alloc_flags, ac,

						mode, &contended_compaction);

	current->flags &= ~PF_MEMALLOC;



	switch (compact_result) {

	case COMPACT_DEFERRED:

		*deferred_compaction = true;

		/* fall-through */

	case COMPACT_SKIPPED:

	if (*compact_result <= COMPACT_INACTIVE)

		return NULL;

	default:

		break;

	}



	/*

	 * At least in one zone compaction wasn't deferred or skipped, so let's
@@ -3233,6 +3225,24 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order, 
	 */

	count_vm_event(COMPACTFAIL);



	/*

	 * In all zones where compaction was attempted (and not

	 * deferred or skipped), lock contention has been detected.

	 * For THP allocation we do not want to disrupt the others

	 * so we fallback to base pages instead.

	 */

	if (contended_compaction == COMPACT_CONTENDED_LOCK)

		*compact_result = COMPACT_CONTENDED;



	/*

	 * If compaction was aborted due to need_resched(), we do not

	 * want to further increase allocation latency, unless it is

	 * khugepaged trying to collapse.

	 */

	if (contended_compaction == COMPACT_CONTENDED_SCHED

		&& !(current->flags & PF_KTHREAD))

		*compact_result = COMPACT_CONTENDED;



	cond_resched();



	return NULL;
@@ -3241,8 +3251,7 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order, 
static inline struct page *

__alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,

		unsigned int alloc_flags, const struct alloc_context *ac,

		enum migrate_mode mode, int *contended_compaction,

		bool *deferred_compaction)

		enum migrate_mode mode, enum compact_result *compact_result)

{

	return NULL;

}
@@ -3387,8 +3396,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, 
	unsigned long pages_reclaimed = 0;

	unsigned long did_some_progress;

	enum migrate_mode migration_mode = MIGRATE_ASYNC;

	bool deferred_compaction = false;

	int contended_compaction = COMPACT_CONTENDED_NONE;

	enum compact_result compact_result;



	/*

	 * In the slowpath, we sanity check order to avoid ever trying to
@@ -3475,8 +3483,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, 
	 */

	page = __alloc_pages_direct_compact(gfp_mask, order, alloc_flags, ac,

					migration_mode,

					&contended_compaction,

					&deferred_compaction);

					&compact_result);

	if (page)

		goto got_pg;
@@ -3489,25 +3496,14 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, 
		 * to heavily disrupt the system, so we fail the allocation

		 * instead of entering direct reclaim.

		 */

		if (deferred_compaction)

		if (compact_result == COMPACT_DEFERRED)

			goto nopage;



		/*

		 * In all zones where compaction was attempted (and not

		 * deferred or skipped), lock contention has been detected.

		 * For THP allocation we do not want to disrupt the others

		 * so we fallback to base pages instead.

		 * Compaction is contended so rather back off than cause

		 * excessive stalls.

		 */

		if (contended_compaction == COMPACT_CONTENDED_LOCK)

			goto nopage;



		/*

		 * If compaction was aborted due to need_resched(), we do not

		 * want to further increase allocation latency, unless it is

		 * khugepaged trying to collapse.

		 */

		if (contended_compaction == COMPACT_CONTENDED_SCHED

			&& !(current->flags & PF_KTHREAD))

		if(compact_result == COMPACT_CONTENDED)

			goto nopage;

	}
@@ -3555,8 +3551,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, 
	 */

	page = __alloc_pages_direct_compact(gfp_mask, order, alloc_flags,

					    ac, migration_mode,

					    &contended_compaction,

					    &deferred_compaction);

					    &compact_result);

	if (page)

		goto got_pg;

nopage: