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Message-ID: <20190627180601.xcppuzia3gk57lq2@box>
Date: Thu, 27 Jun 2019 21:06:01 +0300
From: "Kirill A. Shutemov" <kirill@...temov.name>
To: Minchan Kim <minchan@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
linux-mm <linux-mm@...ck.org>,
LKML <linux-kernel@...r.kernel.org>, linux-api@...r.kernel.org,
Michal Hocko <mhocko@...e.com>,
Johannes Weiner <hannes@...xchg.org>,
Tim Murray <timmurray@...gle.com>,
Joel Fernandes <joel@...lfernandes.org>,
Suren Baghdasaryan <surenb@...gle.com>,
Daniel Colascione <dancol@...gle.com>,
Shakeel Butt <shakeelb@...gle.com>,
Sonny Rao <sonnyrao@...gle.com>, oleksandr@...hat.com,
hdanton@...a.com, lizeb@...gle.com,
Dave Hansen <dave.hansen@...el.com>,
"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH v3 0/5] Introduce MADV_COLD and MADV_PAGEOUT
On Thu, Jun 27, 2019 at 08:54:00PM +0900, Minchan Kim wrote:
> - Problem
>
> Naturally, cached apps were dominant consumers of memory on the system.
> However, they were not significant consumers of swap even though they are
> good candidate for swap. Under investigation, swapping out only begins
> once the low zone watermark is hit and kswapd wakes up, but the overall
> allocation rate in the system might trip lmkd thresholds and cause a cached
> process to be killed(we measured performance swapping out vs. zapping the
> memory by killing a process. Unsurprisingly, zapping is 10x times faster
> even though we use zram which is much faster than real storage) so kill
> from lmkd will often satisfy the high zone watermark, resulting in very
> few pages actually being moved to swap.
Maybe we should look if we do The Right Thing™ at system-wide level before
introducing new API? How changing swappiness affects your workloads? What
is swappiness value in your setup?
--
Kirill A. Shutemov
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