On Wed 10-08-16 11:12:18, Vlastimil Babka wrote:
> COMPACT_PARTIAL has historically meant that compaction returned after doing
> some work without fully compacting a zone. It however didn't distinguish if
> compaction terminated because it succeeded in creating the requested high-order
> page. This has changed recently and now we only return COMPACT_PARTIAL when
> compaction thinks it succeeded, or the high-order watermark check in
> compaction_suitable() passes and no compaction needs to be done.
>
> So at this point we can make the return value clearer by renaming it to
> COMPACT_SUCCESS. The next patch will remove some redundant tests for success
> where compaction just returned COMPACT_SUCCESS.
>
> Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> ---
> include/linux/compaction.h | 8 ++++----
> include/trace/events/compaction.h | 2 +-
> mm/compaction.c | 12 ++++++------
> mm/vmscan.c | 2 +-
> 4 files changed, 12 insertions(+), 12 deletions(-)
>
> diff --git a/include/linux/compaction.h b/include/linux/compaction.h
> index 1bb58581301c..e88c037afe47 100644
> --- a/include/linux/compaction.h
> +++ b/include/linux/compaction.h
> @@ -49,10 +49,10 @@ enum compact_result {
> COMPACT_CONTENDED,
>
> /*
> - * direct compaction partially compacted a zone and there might be
> - * suitable pages
> + * direct compaction terminated after concluding that the allocation
> + * should now succeed
> */
> - COMPACT_PARTIAL,
> + COMPACT_SUCCESS,
> };
>
> struct alloc_context; /* in mm/internal.h */
> @@ -88,7 +88,7 @@ static inline bool compaction_made_progress(enum compact_result result)
> * that the compaction successfully isolated and migrated some
> * pageblocks.
> */
> - if (result == COMPACT_PARTIAL)
> + if (result == COMPACT_SUCCESS)
> return true;
>
> return false;
> diff --git a/include/trace/events/compaction.h b/include/trace/events/compaction.h
> index c2ba402ab256..cbdb90b6b308 100644
> --- a/include/trace/events/compaction.h
> +++ b/include/trace/events/compaction.h
> @@ -13,7 +13,7 @@
> EM( COMPACT_SKIPPED, "skipped") \
> EM( COMPACT_DEFERRED, "deferred") \
> EM( COMPACT_CONTINUE, "continue") \
> - EM( COMPACT_PARTIAL, "partial") \
> + EM( COMPACT_SUCCESS, "success") \
> EM( COMPACT_PARTIAL_SKIPPED, "partial_skipped") \
> EM( COMPACT_COMPLETE, "complete") \
> EM( COMPACT_NO_SUITABLE_PAGE, "no_suitable_page") \
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 328bdfeece2d..c355bf0d8599 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -1329,13 +1329,13 @@ static enum compact_result __compact_finished(struct zone *zone, struct compact_
>
> /* Job done if page is free of the right migratetype */
> if (!list_empty(&area->free_list[migratetype]))
> - return COMPACT_PARTIAL;
> + return COMPACT_SUCCESS;
>
> #ifdef CONFIG_CMA
> /* MIGRATE_MOVABLE can fallback on MIGRATE_CMA */
> if (migratetype == MIGRATE_MOVABLE &&
> !list_empty(&area->free_list[MIGRATE_CMA]))
> - return COMPACT_PARTIAL;
> + return COMPACT_SUCCESS;
> #endif
> /*
> * Job done if allocation would steal freepages from
> @@ -1343,7 +1343,7 @@ static enum compact_result __compact_finished(struct zone *zone, struct compact_
> */
> if (find_suitable_fallback(area, order, migratetype,
> true, &can_steal) != -1)
> - return COMPACT_PARTIAL;
> + return COMPACT_SUCCESS;
> }
>
> return COMPACT_NO_SUITABLE_PAGE;
> @@ -1367,7 +1367,7 @@ static enum compact_result compact_finished(struct zone *zone,
> * compaction_suitable: Is this suitable to run compaction on this zone now?
> * Returns
> * COMPACT_SKIPPED - If there are too few free pages for compaction
> - * COMPACT_PARTIAL - If the allocation would succeed without compaction
> + * COMPACT_SUCCESS - If the allocation would succeed without compaction
> * COMPACT_CONTINUE - If compaction should run now
> */
> static enum compact_result __compaction_suitable(struct zone *zone, int order,
> @@ -1388,7 +1388,7 @@ static enum compact_result __compaction_suitable(struct zone *zone, int order,
> */
> if (zone_watermark_ok(zone, order, watermark, classzone_idx,
> alloc_flags))
> - return COMPACT_PARTIAL;
> + return COMPACT_SUCCESS;
>
> /*
> * Watermarks for order-0 must be met for compaction. Note the 2UL.
> @@ -1477,7 +1477,7 @@ static enum compact_result compact_zone(struct zone *zone, struct compact_contro
> ret = compaction_suitable(zone, cc->order, cc->alloc_flags,
> cc->classzone_idx);
> /* Compaction is likely to fail */
> - if (ret == COMPACT_PARTIAL || ret == COMPACT_SKIPPED)
> + if (ret == COMPACT_SUCCESS || ret == COMPACT_SKIPPED)
> return ret;
>
> /* huh, compaction_suitable is returning something unexpected */
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 374d95d04178..c84784765d3a 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -2514,7 +2514,7 @@ static inline bool should_continue_reclaim(struct pglist_data *pgdat,
> continue;
>
> switch (compaction_suitable(zone, sc->order, 0, sc->reclaim_idx)) {
> - case COMPACT_PARTIAL:
> + case COMPACT_SUCCESS:
> case COMPACT_CONTINUE:
> return false;
> default:
> --
> 2.9.2
>
> --
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--
Michal Hocko
SUSE Labs
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