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authorMichal Hocko <mhocko@suse.com>2016-05-21 02:56:53 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2016-05-21 03:58:30 +0300
commitc5d01d0d18e2ab7a21f0371b00e4d1a06f79cdf5 (patch)
tree5ebb7038a7e113dde69e6a471169cd3e4a6afdcd /mm/page_alloc.c
parent4f9a358c36fcdad3ea1db263ec4d484a70ad543e (diff)
downloadlinux-c5d01d0d18e2ab7a21f0371b00e4d1a06f79cdf5.tar.xz
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: Michal Hocko <mhocko@suse.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Hillf 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: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/page_alloc.c')
-rw-r--r--mm/page_alloc.c67
1 files changed, 31 insertions, 36 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ed62c4b90598..8bcc10616fab 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3185,29 +3185,21 @@ out:
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 @@ retry:
*/
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 @@ retry:
* to heavily disrupt the system, so we fail the allocation
* instead of entering direct reclaim.
*/
- if (deferred_compaction)
- 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.
- */
- if (contended_compaction == COMPACT_CONTENDED_LOCK)
+ if (compact_result == COMPACT_DEFERRED)
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.
+ * Compaction is contended so rather back off than cause
+ * excessive stalls.
*/
- if (contended_compaction == COMPACT_CONTENDED_SCHED
- && !(current->flags & PF_KTHREAD))
+ if(compact_result == COMPACT_CONTENDED)
goto nopage;
}
@@ -3555,8 +3551,7 @@ noretry:
*/
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: