linux-kernel - Re: [PATCH] mm: vmscan: scan anonymous pages on file refaults

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Message-ID: <20190704110425.GD5620@dhcp22.suse.cz>
Date:   Thu, 4 Jul 2019 13:04:25 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Kuo-Hsin Yang <vovoy@...omium.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Minchan Kim <minchan@...nel.org>,
        Sonny Rao <sonnyrao@...omium.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        stable@...r.kernel.org
Subject: Re: [PATCH] mm: vmscan: scan anonymous pages on file refaults

On Thu 04-07-19 17:47:16, Kuo-Hsin Yang wrote:
> On Wed, Jul 03, 2019 at 04:30:57PM +0200, Michal Hocko wrote:
> > 
> > How does the reclaim behave with workloads with file backed data set
> > not fitting into the memory? Aren't we going to to swap a lot -
> > something that the heuristic is protecting from?
> > 
> 
> In common case, most of the pages in a large file backed data set are
> non-executable. When there are a lot of non-executable file pages,
> usually more file pages are scanned because of the recent_scanned /
> recent_rotated ratio.
> 
> I modified the test program to set the accessed sizes of the executable
> and non-executable file pages respectively. The test program runs on 2GB
> RAM VM with kernel 5.2.0-rc7 and this patch, allocates 2000 MB anonymous
> memory, then accesses 100 MB executable file pages and 2100 MB
> non-executable file pages for 10 times. The test also prints the file
> and anonymous page sizes in kB from /proc/meminfo. There are not too
> many swaps in this test case. I got similar test result without this
> patch.

Could you record swap out stats please? Also what happens if you have
multiple readers?

Thanks!
-- 
Michal Hocko
SUSE Labs