linux-kernel - Re: [RFC][PATCHv3] List per-process file descriptor consumption when hitting file-max

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Message-ID: <20100113225715.GE19799@ZenIV.linux.org.uk>
Date:	Wed, 13 Jan 2010 22:57:16 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Alexander Shishkin <virtuoso@...nd.org>
Cc:	Valdis.Kletnieks@...edu, linux-fsdevel@...r.kernel.org,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCHv3] List per-process file descriptor consumption
	when hitting file-max

On Wed, Jan 13, 2010 at 10:44:59PM +0000, Al Viro wrote:
> On Mon, Jan 11, 2010 at 11:38:07AM +0200, Alexander Shishkin wrote:
> > When a file descriptor limit is hit, display the top consumers of
> > descriptors so that it is possible to identify and fix those which
> > leak them.
> > 
> > Two new sysctl tunables are introduced:
> >   * file-max-consumers -- number of processes to display (defaults
> >     to 10);
> >   * file-max-rate-limit -- time interval between subsequent dumps
> >     (defaults to 10 seconds).
> 
> That *still* doesn't answer the most important question: what for?

BTW, even leaving that (and obvious deadlocks) aside, this stuff is
monumentally bogus.  A process can easily have shitloads of opened
descriptors and very few opened files (see dup() and friends).  Conversely,
you can have shitloads of opened files and not a single opened descriptor
(see mmap()).  And you are calling that when we have too many opened
struct file.
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