linux-kernel - Re: [PATCH] mm: compaction: optimize compact

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Message-Id: <20230411134801.a4aadef5aba0f51e0d44bb7a@linux-foundation.org>
Date:   Tue, 11 Apr 2023 13:48:01 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     wenyang.linux@...mail.com
Cc:     Mel Gorman <mgorman@...hsingularity.net>,
        Oscar Salvador <osalvador@...e.de>,
        William Lam <william.lam@...edance.com>,
        Fu Wei <wefu@...hat.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: compaction: optimize compact_memory to comply with
 the admin-guide

On Wed, 12 Apr 2023 02:24:26 +0800 wenyang.linux@...mail.com wrote:

> For the /proc/sys/vm/compact_memory file, the admin-guide states:
> When 1 is written to the file, all zones are compacted such that free
> memory is available in contiguous blocks where possible. This can be
> important for example in the allocation of huge pages although processes
> will also directly compact memory as required
> 
> But it was not strictly followed, writing any value would cause all
> zones to be compacted. In some critical scenarios, some applications
> operating it, such as echo 0, have caused serious problems.

Really?  You mean someone actually did this and didn't observe the
effect during their testing?

> It has been slightly optimized to comply with the admin-guide.