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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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