linux-kernel - Re: [PATCH] mm/ksm: provide global_force to see maximum potential merging

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Message-ID: <YqG/Dyj62aDK/3Jr@dhcp22.suse.cz>
Date:   Thu, 9 Jun 2022 11:36:15 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     cgel.zte@...il.com
Cc:     akpm@...ux-foundation.org, oleksandr@...alenko.name,
        willy@...radead.org, corbet@....net, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-doc@...r.kernel.org,
        xu xin <xu.xin16@....com.cn>
Subject: Re: [PATCH] mm/ksm: provide global_force to see maximum potential
 merging

On Thu 09-06-22 05:56:58, cgel.zte@...il.com wrote:
> From: xu xin <xu.xin16@....com.cn>
> 
> Up to now, KSM is apparently useful to save memory not just for VM but for
> normal applications. But upper application developers might not know much
> about KSM or whether they should use madvise(xxx, MERGEABLE) while there
> indeed exist a lot of same pages in their apps. Some application developers
> urgently need the kernel to provide an interface of KSM debugging mode to
> see the maximum potential merging of the whole system, so the patch is.

I disagree with this. As already discussed in previous proposals of KSM
related interfaces KSM is a nice tool but it shouldn't be used without
understanding of all the consequences.

Maybe we should be more verbose about how to use KSM properly and also
describe best practices but I do not think that enable-for-all in any
form is a good interface.

Nack to the interface.
-- 
Michal Hocko
SUSE Labs