Re: [PATCH 05/11] mm, compaction: distinguish COMPACT_DEFERRED from COMPACT_SKIPPED

[Vlastimil Babka]

On 04/05/2016 01:25 PM, Michal Hocko wrote:
> From: Michal Hocko <mhocko@xxxxxxxx>
>
> try_to_compact_pages can currently return COMPACT_SKIPPED even when the
> compaction is defered for some zone just because zone DMA is skipped
> in 99% of cases due to watermark checks. This makes COMPACT_DEFERRED
> basically unusable for the page allocator as a feedback mechanism.
>
> Make sure we distinguish those two states properly and switch their
> ordering in the enum. This would mean that the COMPACT_SKIPPED will be
> returned only when all eligible zones are skipped.
>
> This shouldn't introduce any functional change.

Hmm, really? __alloc_pages_direct_compact() does distinguish 
COMPACT_DEFERRED, and sets *deferred compaction, so ultimately this is 
some change for THP allocations?

Also there's no mention of COMPACT_INACTIVE in the changelog (which 
indeed isn't functional change, but might surprise somebody).

> Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>

Patch itself is OK.

Acked-by: Vlastimil Babka <vbabka@xxxxxxx>