From: Matthew Wilcox <willy@infradead.org>
To: Stephen Brennan <stephen.s.brennan@oracle.com>,
lsf-pc@lists.linux-foundation.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org
Cc: Gautham Ananthakrishna <gautham.ananthakrishna@oracle.com>,
khlebnikov@yandex-team.ru
Subject: [LSF/MM TOPIC] Better handling of negative dentries
Date: Tue, 15 Mar 2022 19:55:48 +0000 [thread overview]
Message-ID: <YjDvRPuxPN0GsxLB@casper.infradead.org> (raw)
The number of negative dentries is effectively constrained only by memory
size. Systems which do not experience significant memory pressure for
an extended period can build up millions of negative dentries which
clog the dcache. That can have different symptoms, such as inotify
taking a long time [1], high memory usage [2] and even just poor lookup
performance [3]. We've also seen problems with cgroups being pinned
by negative dentries, though I think we now reparent those dentries to
their parent cgroup instead.
We don't have a really good solution yet, and maybe some focused
brainstorming on the problem would lead to something that actually works.
(Apologies to Stephen; I should have thought to send this before the
invitations to LSFMM went out).
[1] https://lore.kernel.org/linux-fsdevel/20220209231406.187668-1-stephen.s.brennan@oracle.com/
[2] https://lore.kernel.org/linux-fsdevel/1611235185-1685-1-git-send-email-gautham.ananthakrishna@oracle.com/
[3] https://lore.kernel.org/linux-fsdevel/158893941613.200862.4094521350329937435.stgit@buzz/
next reply other threads:[~2022-03-15 19:58 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-15 19:55 Matthew Wilcox [this message]
2022-03-15 20:56 ` [LSF/MM TOPIC] Better handling of negative dentries Roman Gushchin
2022-03-16 2:07 ` Gao Xiang
2022-03-16 2:52 ` Dave Chinner
2022-03-16 3:08 ` Gao Xiang
2022-03-22 15:08 ` Matthew Wilcox
2022-03-22 19:19 ` James Bottomley
2022-03-22 20:17 ` Colin Walters
2022-03-22 20:27 ` James Bottomley
2022-03-22 20:37 ` Matthew Wilcox
2022-03-22 21:08 ` Stephen Brennan
2022-03-29 15:24 ` James Bottomley
2022-03-31 19:27 ` Stephen Brennan
2022-04-01 15:45 ` James Bottomley
2022-03-22 22:21 ` Dave Chinner
2022-03-22 20:41 ` Matthew Wilcox
2022-03-22 21:19 ` Roman Gushchin
2022-03-22 22:29 ` Dave Chinner
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