From: Matthew Wilcox <willy@infradead.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Waiman Long <longman@redhat.com>,
Al Viro <viro@zeniv.linux.org.uk>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Jan Kara <jack@suse.cz>,
Paul McKenney <paulmck@linux.vnet.ibm.com>,
Ingo Molnar <mingo@kernel.org>,
Miklos Szeredi <mszeredi@redhat.com>,
Larry Woodman <lwoodman@redhat.com>,
James Bottomley <James.Bottomley@hansenpartnership.com>,
"Wangkai (Kevin,C)" <wangkai86@huawei.com>,
linux-mm@kvack.org, Michal Hocko <mhocko@kernel.org>
Subject: Re: [PATCH v5 0/6] fs/dcache: Track & limit # of negative dentries
Date: Mon, 2 Jul 2018 15:21:05 -0700 [thread overview]
Message-ID: <20180702222105.GA2438@bombadil.infradead.org> (raw)
In-Reply-To: <20180702141811.ef027fd7d8087b7fb2ba0cce@linux-foundation.org>
On Mon, Jul 02, 2018 at 02:18:11PM -0700, Andrew Morton wrote:
> In the [5/6] changelog it is mentioned that a large number of -ve
> dentries can lead to oom-killings. This sounds bad - -ve dentries
> should be trivially reclaimable and we shouldn't be oom-killing in such
> a situation.
>
> Dumb question: do we know that negative dentries are actually
> worthwhile? Has anyone checked in the past couple of decades? Perhaps
> our lookups are so whizzy nowadays that we don't need them?
I can't believe that's true. Have you looked at strace of a typical
program startup recently?
$ strace -o ls.out ls
$ grep -c ENOENT ls.out
10
There's a few duplicates in there (6 accesses to /etc/ld.so.nohwcap), so
we definitely want those negative entries.
next prev parent reply other threads:[~2018-07-02 22:21 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-02 5:51 [PATCH v5 0/6] fs/dcache: Track & limit # of negative dentries Waiman Long
2018-07-02 5:51 ` [PATCH v5 1/6] fs/dcache: Track & report number " Waiman Long
2018-07-02 5:51 ` [PATCH v5 2/6] fs/dcache: Make negative dentry tracking configurable Waiman Long
2018-07-02 21:12 ` Andrew Morton
2018-07-03 0:59 ` Waiman Long
2018-07-02 5:52 ` [PATCH v5 3/6] fs/dcache: Enable automatic pruning of negative dentries Waiman Long
2018-07-02 5:52 ` [PATCH v5 4/6] fs/dcache: Spread negative dentry pruning across multiple CPUs Waiman Long
2018-07-02 5:52 ` [PATCH v5 5/6] fs/dcache: Allow optional enforcement of negative dentry limit Waiman Long
2018-07-02 5:52 ` [PATCH v5 6/6] fs/dcache: Make negative dentry limit enforcement sysctl parameter Waiman Long
2018-07-02 19:34 ` [PATCH v5 0/6] fs/dcache: Track & limit # of negative dentries Linus Torvalds
2018-07-02 21:18 ` Andrew Morton
2018-07-02 22:21 ` Matthew Wilcox [this message]
2018-07-02 22:31 ` Linus Torvalds
2018-07-02 22:34 ` James Bottomley
2018-07-02 22:54 ` Linus Torvalds
2018-07-02 23:03 ` Linus Torvalds
2018-07-02 23:19 ` Andrew Morton
2018-07-02 23:28 ` Linus Torvalds
2018-07-03 1:38 ` Waiman Long
2018-07-03 9:18 ` Jan Kara
2018-07-14 17:35 ` Pavel Machek
2018-07-14 18:00 ` Linus Torvalds
2018-07-14 18:34 ` Al Viro
2018-07-14 18:36 ` Al Viro
2018-07-14 18:43 ` Linus Torvalds
2018-07-18 16:01 ` Waiman Long
2018-07-03 1:11 ` Waiman Long
2018-07-03 13:48 ` Vlastimil Babka
2018-07-03 0:46 ` Waiman Long
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