From: Vlastimil Babka <vbabka@suse.cz>
To: Jann Horn <jannh@google.com>, Christoph Lameter <cl@linux.com>,
Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Andrew Morton <akpm@linux-foundation.org>
Cc: Linux-MM <linux-mm@kvack.org>,
kernel list <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Roman Gushchin <guro@fb.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Shakeel Butt <shakeelb@google.com>,
Suren Baghdasaryan <surenb@google.com>,
Minchan Kim <minchan@kernel.org>,
Michal Hocko <mhocko@kernel.org>
Subject: Re: SLUB: percpu partial object count is highly inaccurate, causing some memory wastage and maybe also worse tail latencies?
Date: Thu, 21 Jan 2021 18:21:18 +0100 [thread overview]
Message-ID: <aa02cf86-3a83-2e55-3bb6-3ec1c0f71b11@suse.cz> (raw)
In-Reply-To: <CAG48ez2Qx5K1Cab-m8BdSibp6wLTip6ro4=-umR7BLsEgjEYzA@mail.gmail.com>
On 1/12/21 12:12 AM, Jann Horn wrote:
> At first I thought that this wasn't a significant issue because SLUB
> has a reclaim path that can trim the percpu partial lists; but as it
> turns out, that reclaim path is not actually wired up to the page
> allocator's reclaim logic. The SLUB reclaim stuff is only triggered by
> (very rare) subsystem-specific calls into SLUB for specific slabs and
> by sysfs entries. So in userland processes will OOM even if SLUB still
> has megabytes of entirely unused pages lying around.
>
> It might be a good idea to figure out whether it is possible to
> efficiently keep track of a more accurate count of the free objects on
> percpu partial lists; and if not, maybe change the accounting to
> explicitly track the number of partial pages, and use limits that are
> more appropriate for that? And perhaps the page allocator reclaim path
> should also occasionally rip unused pages out of the percpu partial
> lists?
I'm gonna send a RFC that adds a proper shrinker and thus connects this
shrinking to page reclaim, as a reply to this e-mail.
next prev parent reply other threads:[~2021-01-21 17:21 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-11 23:12 SLUB: percpu partial object count is highly inaccurate, causing some memory wastage and maybe also worse tail latencies? Jann Horn
2021-01-12 0:27 ` Roman Gushchin
2021-01-12 16:35 ` Christoph Lameter
2021-01-14 9:27 ` Vlastimil Babka
2021-01-18 11:03 ` Michal Hocko
2021-01-18 15:46 ` Christoph Lameter
2021-01-18 16:07 ` Michal Hocko
2021-01-13 19:14 ` Vlastimil Babka
2021-01-13 22:37 ` Jann Horn
2021-01-14 9:04 ` Christoph Lameter
2021-01-21 17:21 ` Vlastimil Babka [this message]
2021-01-21 17:21 ` [RFC 1/2] mm, vmscan: add priority field to struct shrink_control Vlastimil Babka
2021-01-21 17:21 ` [RFC 2/2] mm, slub: add shrinker to reclaim cached slabs Vlastimil Babka
2021-01-22 0:48 ` Roman Gushchin
2021-01-26 12:06 ` Vlastimil Babka
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