linux-kernel - Re: [PATCH] mm/madvise: fix madvise_pageout for private file mappings

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Message-ID: <20221201030045.GB3980@hu-pkondeti-hyd.qualcomm.com>
Date:   Thu, 1 Dec 2022 08:30:45 +0530
From:   Pavan Kondeti <quic_pkondeti@...cinc.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
CC:     Pavankumar Kondeti <quic_pkondeti@...cinc.com>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Minchan Kim <minchan@...nel.org>,
        Charan Teja Kalla <quic_charante@...cinc.com>,
        Prakash Gupta <quic_guptap@...cinc.com>,
        Divyanand Rangu <quic_drangu@...cinc.com>
Subject: Re: [PATCH] mm/madvise: fix madvise_pageout for private file mappings

On Wed, Nov 30, 2022 at 03:17:39PM -0800, Andrew Morton wrote:
> 
> On Wed, 9 Nov 2022 10:48:36 +0530 Pavankumar Kondeti <quic_pkondeti@...cinc.com> wrote:
> 
> > When MADV_PAGEOUT is called on a private file mapping VMA region,
> > we bail out early if the process is neither owner nor write capable
> > of the file. However, this VMA may have both private/shared clean
> > pages and private dirty pages. The opportunity of paging out the
> > private dirty pages (Anon pages) is missed. Fix this by caching
> > the file access check and use it later along with PageAnon() during
> > page walk.
> > 
> > We observe ~10% improvement in zram usage, thus leaving more available
> > memory on a 4GB RAM system running Android.
> > 
> 
> Could we please have some reviewer input on this?
> 
> Thanks.
> 

Thanks Andrew for the reminder. Fyi, this patch has been included in Android
Generic Kernel Image (5.10 and 5.15 kernels) as we have seen good savings on
Android. It would make a difference on a low memory android devices.

Suren/Minchan,

Can you please do the needful?

Thanks,
Pavan