>
> From: Michal Hocko <mhocko@xxxxxxxx>
>
> COMPACT_COMPLETE now means that compaction and free scanner met. This is
> not very useful information if somebody just wants to use this feedback
> and make any decisions based on that. The current caller might be a poor
> guy who just happened to scan tiny portion of the zone and that could be
> the reason no suitable pages were compacted. Make sure we distinguish
> the full and partial zone walks.
>
> Consumers should treat COMPACT_PARTIAL_SKIPPED as a potential success
> and be optimistic in retrying.
>
> The existing users of COMPACT_COMPLETE are conservatively changed to
> use COMPACT_PARTIAL_SKIPPED as well but some of them should be probably
> reconsidered and only defer the compaction only for COMPACT_COMPLETE
> with the new semantic.
>
> This patch shouldn't introduce any functional changes.
>
> Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
> Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
> ---
Acked-by: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx>
> include/linux/compaction.h | 10 +++++++++-
> include/trace/events/compaction.h | 1 +
> mm/compaction.c | 14 +++++++++++---
> mm/internal.h | 1 +
> 4 files changed, 22 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/compaction.h b/include/linux/compaction.h
> index 7e177d111c39..7c4de92d12cc 100644
> --- a/include/linux/compaction.h
> +++ b/include/linux/compaction.h
> @@ -21,7 +21,15 @@ enum compact_result {
> * pages
> */
> COMPACT_PARTIAL,
> - /* The full zone was compacted */
> + /*
> + * direct compaction has scanned part of the zone but wasn't successfull
> + * to compact suitable pages.
> + */
> + COMPACT_PARTIAL_SKIPPED,
> + /*
> + * The full zone was compacted scanned but wasn't successfull to compact
> + * suitable pages.
> + */
> COMPACT_COMPLETE,
> /* For more detailed tracepoint output */
> COMPACT_NO_SUITABLE_PAGE,
> diff --git a/include/trace/events/compaction.h b/include/trace/events/compaction.h
> index 6ba16c86d7db..36e2d6fb1360 100644
> --- a/include/trace/events/compaction.h
> +++ b/include/trace/events/compaction.h
> @@ -14,6 +14,7 @@
> EM( COMPACT_DEFERRED, "deferred") \
> EM( COMPACT_CONTINUE, "continue") \
> EM( COMPACT_PARTIAL, "partial") \
> + EM( COMPACT_PARTIAL_SKIPPED, "partial_skipped") \
> EM( COMPACT_COMPLETE, "complete") \
> EM( COMPACT_NO_SUITABLE_PAGE, "no_suitable_page") \
> EM( COMPACT_NOT_SUITABLE_ZONE, "not_suitable_zone") \
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 13709e33a2fc..e2e487cea5ea 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -1304,7 +1304,10 @@ static enum compact_result __compact_finished(struct zone *zone, struct compact_
> if (cc->direct_compaction)
> zone->compact_blockskip_flush = true;
>
> - return COMPACT_COMPLETE;
> + if (cc->whole_zone)
> + return COMPACT_COMPLETE;
> + else
> + return COMPACT_PARTIAL_SKIPPED;
> }
>
> if (is_via_compact_memory(cc->order))
> @@ -1463,6 +1466,10 @@ static enum compact_result compact_zone(struct zone *zone, struct compact_contro
> zone->compact_cached_migrate_pfn[0] = cc->migrate_pfn;
> zone->compact_cached_migrate_pfn[1] = cc->migrate_pfn;
> }
> +
> + if (cc->migrate_pfn == start_pfn)
> + cc->whole_zone = true;
> +
> cc->last_migrated_pfn = 0;
>
> trace_mm_compaction_begin(start_pfn, cc->migrate_pfn,
> @@ -1693,7 +1700,8 @@ enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order,
> goto break_loop;
> }
>
> - if (mode != MIGRATE_ASYNC && status == COMPACT_COMPLETE) {
> + if (mode != MIGRATE_ASYNC && (status == COMPACT_COMPLETE ||
> + status == COMPACT_PARTIAL_SKIPPED)) {
> /*
> * We think that allocation won't succeed in this zone
> * so we defer compaction there. If it ends up
> @@ -1939,7 +1947,7 @@ static void kcompactd_do_work(pg_data_t *pgdat)
> cc.classzone_idx, 0)) {
> success = true;
> compaction_defer_reset(zone, cc.order, false);
> - } else if (status == COMPACT_COMPLETE) {
> + } else if (status == COMPACT_PARTIAL_SKIPPED || status == COMPACT_COMPLETE) {
> /*
> * We use sync migration mode here, so we defer like
> * sync direct compaction does.
> diff --git a/mm/internal.h b/mm/internal.h
> index e9aacea1a0d1..4423dfe69382 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -182,6 +182,7 @@ struct compact_control {
> enum migrate_mode mode; /* Async or sync migration mode */
> bool ignore_skip_hint; /* Scan blocks even if marked skip */
> bool direct_compaction; /* False from kcompactd or /proc/... */
> + bool whole_zone; /* Whole zone has been scanned */
> int order; /* order a direct compactor needs */
> const gfp_t gfp_mask; /* gfp mask of a direct compactor */
> const int alloc_flags; /* alloc flags of a direct compactor */
> --
> 2.8.0.rc3
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