linux-kernel - Re: [PATCH v3 0/5] ksm: support tracking KSM-placed zero-pages

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Message-Id: <20221018155407.41c993924ec09a64ae966d50@linux-foundation.org>
Date:   Tue, 18 Oct 2022 15:54:07 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     xu xin <xu.xin.sc@...il.com>
Cc:     david@...hat.com, imbrenda@...ux.ibm.com, jiang.xuexin@....com.cn,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        ran.xiaokai@....com.cn, xu.xin16@....com.cn, yang.yang29@....com.cn
Subject: Re: [PATCH v3 0/5] ksm: support tracking KSM-placed zero-pages

On Tue, 18 Oct 2022 09:00:22 +0000 xu xin <xu.xin.sc@...il.com> wrote:

> >A full description of the real-world end-user operational benefits of
> >these changes would help, please.
> >
> 
> The core idea of this patch set is to enable users to perceive the number of any
> pages merged by KSM, regardless of whether use_zero_page switch has been turned
> on, so that users can know how much free memory increase is really due to their
> madvise(MERGEABLE) actions.

OK, thanks.

> The motivation for me to do this is that when I do
> an application optimization of KSM on embedded Linux for 5G platform, I find
> that ksm_merging_pages of some process becomes very small(but used to be large),
> which led me to think that there was any problem with the application KSM-madvise
> strategy, but in fact, it was only because use_zero_pages is on.

Please expand on the above motivation and experience, and include it in
the [0/n] changelog.  But let's leave it a few days to see if there's
additional reviewer input.