From: Ian Kent <raven@themaw.net>
To: Al Viro <viro@zeniv.linux.org.uk>, Matthew Wilcox <willy@infradead.org>
Cc: Andreas Dilger <adilger@dilger.ca>,
Waiman Long <longman@redhat.com>,
Jonathan Corbet <corbet@lwn.net>,
Luis Chamberlain <mcgrof@kernel.org>,
Kees Cook <keescook@chromium.org>,
Iurii Zaikin <yzaikin@google.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux FS Devel <linux-fsdevel@vger.kernel.org>,
linux-doc@vger.kernel.org,
Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
Eric Biggers <ebiggers@google.com>,
Dave Chinner <david@fromorbit.com>,
Eric Sandeen <sandeen@redhat.com>
Subject: Re: [PATCH 00/11] fs/dcache: Limit # of negative dentries
Date: Fri, 28 Feb 2020 12:52:52 +0800 [thread overview]
Message-ID: <2b03788f9d71d9d972cbe908e0f0fb0e37672719.camel@themaw.net> (raw)
In-Reply-To: <20200228042208.GI23230@ZenIV.linux.org.uk>
On Fri, 2020-02-28 at 04:22 +0000, Al Viro wrote:
> On Thu, Feb 27, 2020 at 07:34:12PM -0800, Matthew Wilcox wrote:
> > On Thu, Feb 27, 2020 at 05:55:43PM +0800, Ian Kent wrote:
> > > Not all file systems even produce negative hashed dentries.
> > >
> > > The most beneficial use of them is to improve performance of
> > > rapid
> > > fire lookups for non-existent names. Longer lived negative hashed
> > > dentries don't give much benefit at all unless they suddenly have
> > > lots of hits and that would cost a single allocation on the first
> > > lookup if the dentry ttl expired and the dentry discarded.
> > >
> > > A ttl (say jiffies) set at appropriate times could be a better
> > > choice all round, no sysctl values at all.
> >
> > The canonical argument in favour of negative dentries is to improve
> > application startup time as every application searches the library
> > path
> > for the same libraries. Only they don't do that any more:
>
> Tell that to scripts that keep looking through $PATH for
> binaries each time they are run. Tell that to cc(1) looking through
> include path, etc.
>
> Ian, autofs is deeply pathological in that respect; that's OK,
> since it has very unusual needs, but please don't use it as a model
> for anything else - its needs *are* unusual.
Ok, but my thoughts aren't based on autofs behaviours.
But it sounds like you don't believe this is a sensible suggestion
and you would know best so ...
Ian
next prev parent reply other threads:[~2020-02-28 4:53 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-26 16:13 [PATCH 00/11] fs/dcache: Limit # of negative dentries Waiman Long
2020-02-26 16:13 ` [PATCH 01/11] fs/dcache: Fix incorrect accounting " Waiman Long
2020-02-26 16:13 ` [PATCH 02/11] fs/dcache: Simplify __dentry_kill() Waiman Long
2020-02-26 16:13 ` [PATCH 03/11] fs/dcache: Add a counter to track number of children Waiman Long
2020-02-26 16:13 ` [PATCH 04/11] fs/dcache: Add sysctl parameter dentry-dir-max Waiman Long
2020-02-26 16:13 ` [PATCH 05/11] fs/dcache: Reclaim excessive negative dentries in directories Waiman Long
2020-02-26 16:13 ` [PATCH 06/11] fs/dcache: directory opportunistically stores # of positive dentries Waiman Long
2020-02-26 16:14 ` [PATCH 07/11] fs/dcache: Add static key negative_reclaim_enable Waiman Long
2020-02-26 16:14 ` [PATCH 08/11] fs/dcache: Limit dentry reclaim count in negative_reclaim_workfn() Waiman Long
2020-02-26 16:14 ` [PATCH 09/11] fs/dcache: Don't allow small values for dentry-dir-max Waiman Long
2020-02-26 16:14 ` [PATCH 10/11] fs/dcache: Kill off dentry as last resort Waiman Long
2020-02-26 16:14 ` [PATCH 11/11] fs/dcache: Track # of negative dentries reclaimed & killed Waiman Long
2020-02-26 16:29 ` [PATCH 00/11] fs/dcache: Limit # of negative dentries Matthew Wilcox
2020-02-26 19:19 ` Waiman Long
2020-02-26 21:28 ` Matthew Wilcox
2020-02-26 21:28 ` Andreas Dilger
2020-02-26 21:45 ` Matthew Wilcox
2020-02-27 8:07 ` Dave Chinner
2020-02-27 9:55 ` Ian Kent
2020-02-28 3:34 ` Matthew Wilcox
2020-02-28 4:16 ` Ian Kent
2020-02-28 4:36 ` Ian Kent
2020-02-28 4:52 ` Al Viro
2020-02-28 4:22 ` Al Viro
2020-02-28 4:52 ` Ian Kent [this message]
2020-02-28 15:32 ` Waiman Long
2020-02-28 15:39 ` Matthew Wilcox
2020-02-28 19:32 ` Theodore Y. Ts'o
2020-02-27 19:04 ` Eric Sandeen
2020-02-27 22:39 ` Dave Chinner
2020-02-27 8:30 ` Dave Chinner
2020-02-28 15:47 ` Waiman Long
2020-03-15 3:46 ` Matthew Wilcox
2020-03-21 10:17 ` Konstantin Khlebnikov
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