linux-kernel - Re: [PATCH v6 0/6] ksm: support tracking KSM-placed zero-pages

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Message-ID: <20230414104053.7c57a4f6@p-imbrenda>
Date:   Fri, 14 Apr 2023 10:40:53 +0200
From:   Claudio Imbrenda <imbrenda@...ux.ibm.com>
To:     xu xin <xu.xin.sc@...il.com>
Cc:     akpm@...ux-foundation.org, david@...hat.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 v6 0/6] ksm: support tracking KSM-placed zero-pages

On Fri, 14 Apr 2023 09:35:07 +0800
xu xin <xu.xin.sc@...il.com> wrote:

> >> 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. But the problem is, when enabling use_zero_pages,
> >> all empty pages will be merged with kernel zero pages instead of with each
> >> other as use_zero_pages is disabled, and then these zero-pages are no longer
> >> monitored by KSM.  
> >  
> 
> We have sent the v7 series, so some old codes might be changed, and no need to talk
> more.
> 
> >We appear to have some outstanding activity on this quite old patchset.
> >From my notes:
> >
> >- An unresponded-to question from Claudia:
> >	https://lkml.kernel.org/r/20230307192421.30ab869c@p-imbrenda
> >  
> 
> Claudia is right, but the v7 patches don't rely on rmap_items now, so we can skip
> this comment.
> 
> >- Hoping for overall review from David
> >  
> 
> David's review is great, and we accept his advice on the basic approach in v7 patches
> to track the ksm zero pages. and now the v7 patches use pte_dirty to mark the
> KSM-placed zere pages. But since pte_dirty is related to architectures, and some
> architecture may treat pte_dirty as writable, so we restrict the feature of tracking
> ksm zero pages only to the tested and well-working architecture.
> 
> >- Another query from Claudia, and a response indicating that a v7 is
> >  in the works.
> >	https://lore.kernel.org/all/20230307194320.79373a26@p-imbrenda/T/#u  
> 
> The v7 series don't changed it there now, then we can skip it.
> 
> >
> >- Another unresponded-to review query:
> >	https://lkml.kernel.org/r/20230307195119.745d0b46@p-imbrenda
> >  
> 
> The v7 series have referred to Claudia's review but made a few modifications.

I would just like to point out that my name is Claudio, not
Claudia. (this goes to Andrew as well)


thanks

> 
> >- Another response indicating that a v7 is coming
> >	https://lkml.kernel.org/r/20230307195313.2e21245a@p-imbrenda
> >
> > So I think I'll drop the v6 series.  Please address all these things in
> > the next version and let's start over.  
> 
> Yes, the next version is here:
> https://lore.kernel.org/lkml/202304131346489021903@zte.com.cn/
> 
>