>
> From: Michal Hocko <mho...@suse.com>
>
> compaction_result will be used as the primary feedback channel for
> compaction users. At the same time try_to_compact_pages (and potentially
> others) assume a certain ordering where a more specific feedback takes
> precendence. This gets a bit awkward when we have conflicting feedback
> from different zones. E.g one returing COMPACT_COMPLETE meaning the full
> zone has been scanned without any outcome while other returns with
> COMPACT_PARTIAL aka made some progress. The caller should get
> COMPACT_PARTIAL because that means that the compaction still can make
> some progress. The same applies for COMPACT_PARTIAL vs.
> COMPACT_PARTIAL_SKIPPED. Reorder PARTIAL to be the largest one so the
> larger the value is the more progress we have done.
>
> Acked-by: Vlastimil Babka <vba...@suse.cz>
> Signed-off-by: Michal Hocko <mho...@suse.com>
> ---
Acked-by: Hillf Danton <hillf...@alibaba-inc.com>
> include/linux/compaction.h | 26 ++++++++++++++++----------
> 1 file changed, 16 insertions(+), 10 deletions(-)
>
> diff --git a/include/linux/compaction.h b/include/linux/compaction.h
> index 7c4de92d12cc..a7b9091ff349 100644
> --- a/include/linux/compaction.h
> +++ b/include/linux/compaction.h
> @@ -4,6 +4,8 @@
> /* Return values for compact_zone() and try_to_compact_pages() */
> /* When adding new states, please adjust include/trace/events/compaction.h */
> enum compact_result {
> + /* For more detailed tracepoint output - internal to compaction */
> + COMPACT_NOT_SUITABLE_ZONE,
> /*
> * compaction didn't start as it was not possible or direct reclaim
> * was more suitable
> @@ -11,30 +13,34 @@ enum compact_result {
> COMPACT_SKIPPED,
> /* compaction didn't start as it was deferred due to past failures */
> COMPACT_DEFERRED,
> +
> /* compaction not active last round */
> COMPACT_INACTIVE = COMPACT_DEFERRED,
>
> + /* For more detailed tracepoint output - internal to compaction */
> + COMPACT_NO_SUITABLE_PAGE,
> /* compaction should continue to another pageblock */
> COMPACT_CONTINUE,
> +
> /*
> - * direct compaction partially compacted a zone and there are suitable
> - * pages
> + * The full zone was compacted scanned but wasn't successfull to compact
> + * suitable pages.
> */
> - COMPACT_PARTIAL,
> + COMPACT_COMPLETE,
> /*
> * direct compaction has scanned part of the zone but wasn't successfull
> * to compact suitable pages.
> */
> COMPACT_PARTIAL_SKIPPED,
> +
> + /* compaction terminated prematurely due to lock contentions */
> + COMPACT_CONTENDED,
> +
> /*
> - * The full zone was compacted scanned but wasn't successfull to compact
> - * suitable pages.
> + * direct compaction partially compacted a zone and there might be
> + * suitable pages
> */
> - COMPACT_COMPLETE,
> - /* For more detailed tracepoint output */
> - COMPACT_NO_SUITABLE_PAGE,
> - COMPACT_NOT_SUITABLE_ZONE,
> - COMPACT_CONTENDED,
> + COMPACT_PARTIAL,
> };
>
> /* Used to signal whether compaction detected need_sched() or lock
> contention */
> --
> 2.8.0.rc3
