Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Tue, 11 Apr 2023 13:48:01 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     wenyang.linux@foxmail.com
Cc:     Mel Gorman <mgorman@techsingularity.net>,
        Oscar Salvador <osalvador@suse.de>,
        William Lam <william.lam@bytedance.com>,
        Fu Wei <wefu@redhat.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: compaction: optimize compact_memory to comply with
 the admin-guide
Message-Id: <20230411134801.a4aadef5aba0f51e0d44bb7a@linux-foundation.org>
In-Reply-To: <tencent_FD958236269FD3A7996FFCF29E9BAA4EA809@qq.com>
References: <tencent_FD958236269FD3A7996FFCF29E9BAA4EA809@qq.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Precedence: bulk

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