The patch titled
Subject: mm, compaction: Abstract compaction feedback to helpers
has been added to the -mm tree. Its filename is
mm-compaction-abstract-compaction-feedback-to-helpers.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-compaction-abstract-compaction-feedback-to-helpers.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-compaction-abstract-compaction-feedback-to-helpers.patch
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From: Michal Hocko <mhocko@xxxxxxxx>
Subject: mm, compaction: Abstract compaction feedback to helpers
Compaction can provide a wild variation of feedback to the caller. Many
of them are implementation specific and the caller of the compaction
(especially the page allocator) shouldn't be bound to specifics of the
current implementation.
This patch abstracts the feedback into three basic types:
- compaction_made_progress - compaction was active and made some
progress.
- compaction_failed - compaction failed and further attempts to
invoke it would most probably fail and therefore it is not
worth retrying
- compaction_withdrawn - compaction wasn't invoked for an
implementation specific reasons. In the current implementation
it means that the compaction was deferred, contended or the
page scanners met too early without any progress. Retrying is
still worthwhile.
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx>
Cc: Joonsoo Kim <js1304@xxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/compaction.h | 74 +++++++++++++++++++++++++++++++++++
mm/page_alloc.c | 25 ++---------
2 files changed, 80 insertions(+), 19 deletions(-)
diff -puN include/linux/compaction.h~mm-compaction-abstract-compaction-feedback-to-helpers include/linux/compaction.h
--- a/include/linux/compaction.h~mm-compaction-abstract-compaction-feedback-to-helpers
+++ a/include/linux/compaction.h
@@ -78,6 +78,70 @@ extern void compaction_defer_reset(struc
bool alloc_success);
extern bool compaction_restarting(struct zone *zone, int order);
+/* Compaction has made some progress and retrying makes sense */
+static inline bool compaction_made_progress(enum compact_result result)
+{
+ /*
+ * Even though this might sound confusing this in fact tells us
+ * that the compaction successfully isolated and migrated some
+ * pageblocks.
+ */
+ if (result == COMPACT_PARTIAL)
+ return true;
+
+ return false;
+}
+
+/* Compaction has failed and it doesn't make much sense to keep retrying. */
+static inline bool compaction_failed(enum compact_result result)
+{
+ /* All zones where scanned completely and still not result. */
+ if (result == COMPACT_COMPLETE)
+ return true;
+
+ return false;
+}
+
+/*
+ * Compaction has backed off for some reason. It might be throttling or
+ * lock contention. Retrying is still worthwhile.
+ */
+static inline bool compaction_withdrawn(enum compact_result result)
+{
+ /*
+ * Compaction backed off due to watermark checks for order-0
+ * so the regular reclaim has to try harder and reclaim something.
+ */
+ if (result == COMPACT_SKIPPED)
+ return true;
+
+ /*
+ * If compaction is deferred for high-order allocations, it is
+ * because sync compaction recently failed. If this is the case
+ * and the caller requested a THP allocation, we do not want
+ * to heavily disrupt the system, so we fail the allocation
+ * instead of entering direct reclaim.
+ */
+ if (result == COMPACT_DEFERRED)
+ return true;
+
+ /*
+ * If compaction in async mode encounters contention or blocks higher
+ * priority task we back off early rather than cause stalls.
+ */
+ if (result == COMPACT_CONTENDED)
+ return true;
+
+ /*
+ * Page scanners have met but we haven't scanned full zones so this
+ * is a back off in fact.
+ */
+ if (result == COMPACT_PARTIAL_SKIPPED)
+ return true;
+
+ return false;
+}
+
extern int kcompactd_run(int nid);
extern void kcompactd_stop(int nid);
extern void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx);
@@ -113,6 +177,16 @@ static inline bool compaction_deferred(s
{
return true;
}
+
+static inline bool compaction_made_progress(enum compact_result result)
+{
+ return false;
+}
+
+static inline bool compaction_withdrawn(enum compact_result result)
+{
+ return true;
+}
static inline int kcompactd_run(int nid)
{
diff -puN mm/page_alloc.c~mm-compaction-abstract-compaction-feedback-to-helpers mm/page_alloc.c
--- a/mm/page_alloc.c~mm-compaction-abstract-compaction-feedback-to-helpers
+++ a/mm/page_alloc.c
@@ -3366,25 +3366,12 @@ retry:
if (page)
goto got_pg;
- /* Checks for THP-specific high-order allocations */
- if (is_thp_gfp_mask(gfp_mask)) {
- /*
- * If compaction is deferred for high-order allocations, it is
- * because sync compaction recently failed. If this is the case
- * and the caller requested a THP allocation, we do not want
- * to heavily disrupt the system, so we fail the allocation
- * instead of entering direct reclaim.
- */
- if (compact_result == COMPACT_DEFERRED)
- goto nopage;
-
- /*
- * Compaction is contended so rather back off than cause
- * excessive stalls.
- */
- if(compact_result == COMPACT_CONTENDED)
- goto nopage;
- }
+ /*
+ * Checks for THP-specific high-order allocations and back off
+ * if the the compaction backed off
+ */
+ if (is_thp_gfp_mask(gfp_mask) && compaction_withdrawn(compact_result))
+ goto nopage;
/*
* It can become very expensive to allocate transparent hugepages at
_
Patches currently in -mm which might be from mhocko@xxxxxxxx are
include-linux-nodemaskh-create-next_node_in-helper-fix.patch
mm-oom-rework-oom-detection.patch
mm-throttle-on-io-only-when-there-are-too-many-dirty-and-writeback-pages.patch
mm-compaction-change-compact_-constants-into-enum.patch
mm-compaction-cover-all-compaction-mode-in-compact_zone.patch
mm-compaction-distinguish-compact_deferred-from-compact_skipped.patch
mm-compaction-distinguish-between-full-and-partial-compact_complete.patch
mm-compaction-update-compaction_result-ordering.patch
mm-compaction-simplify-__alloc_pages_direct_compact-feedback-interface.patch
mm-compaction-abstract-compaction-feedback-to-helpers.patch
mm-oom-protect-costly-allocations-some-more.patch
mm-consider-compaction-feedback-also-for-costly-allocation.patch
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