linux-kernel - Re: [PATCH V2] mm: compaction: update the COMPACT[STALL|FAIL] events properly

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Date:   Fri, 12 Feb 2021 13:16:48 -0800 (PST)
From:   David Rientjes <rientjes@...gle.com>
To:     Charan Teja Reddy <charante@...eaurora.org>
cc:     akpm@...ux-foundation.org, vbabka@...e.cz, linux-mm@...ck.org,
        vinmenon@...eaurora.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] mm: compaction: update the COMPACT[STALL|FAIL] events
 properly

On Fri, 12 Feb 2021, Charan Teja Reddy wrote:

> By definition, COMPACT[STALL|FAIL] events needs to be counted when there
> is 'At least in one zone compaction wasn't deferred or skipped from the
> direct compaction'. And when compaction is skipped or deferred,
> COMPACT_SKIPPED will be returned but it will still go and update these
> compaction events which is wrong in the sense that COMPACT[STALL|FAIL]
> is counted without even trying the compaction.
> 
> Correct this by skipping the counting of these events when
> COMPACT_SKIPPED is returned for compaction. This indirectly also avoid
> the unnecessary try into the get_page_from_freelist() when compaction is
> not even tried.
> 
> There is a corner case where compaction is skipped but still count
> COMPACTSTALL event, which is that IRQ came and freed the page and the
> same is captured in capture_control.
> 
> Signed-off-by: Charan Teja Reddy <charante@...eaurora.org>

Acked-by: David Rientjes <rientjes@...gle.com>