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Date:   Sun, 25 Jul 2021 18:47:18 -0700 (PDT)
From:   David Rientjes <rientjes@google.com>
To:     Charan Teja Reddy <charante@codeaurora.org>
cc:     akpm@linux-foundation.org, vbabka@suse.cz, nigupta@nvidia.com,
        khalid.aziz@oracle.com, vinmenon@codeaurora.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH resend] mm: compaction: optimize proactive compaction
 deferrals
In-Reply-To: <1626869599-25412-1-git-send-email-charante@codeaurora.org>
Message-ID: <83f046a3-5afc-fe6d-40dc-d7aee7b7e398@google.com>
References: <1626869599-25412-1-git-send-email-charante@codeaurora.org>
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On Wed, 21 Jul 2021, Charan Teja Reddy wrote:

> Vlastimil Babka figured out that when fragmentation score didn't go down
> across the proactive compaction i.e. when no progress is made, next wake
> up for proactive compaction is deferred for 1 <<
> COMPACT_MAX_DEFER_SHIFT, i.e. 64 times, with each wakeup interval of
> HPAGE_FRAG_CHECK_INTERVAL_MSEC(=500). In each of this wakeup, it just
> decrement 'proactive_defer' counter and goes sleep i.e. it is getting
> woken to just decrement a counter. The same deferral time can also
> achieved by simply doing the HPAGE_FRAG_CHECK_INTERVAL_MSEC <<
> COMPACT_MAX_DEFER_SHIFT thus unnecessary wakeup of kcompact thread is
> avoided thus also removes the need of 'proactive_defer' thread counter.
> 
> Link: https://lore.kernel.org/linux-fsdevel/88abfdb6-2c13-b5a6-5b46-742d12d1c910@suse.cz/
> Signed-off-by: Charan Teja Reddy <charante@codeaurora.org>

With Andrew's comment fixup:

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

Thanks, Charan.