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From: Andrew Morton <akpm@digeo.com>
To: Matthew Wilcox <willy@debian.org>
Cc: linux-fsdevel@vger.kernel.org, dwmw2@infradead.org, wli@holomorphy.com
Subject: Re: simultaneous creates in a directory
Date: Fri, 27 Sep 2002 12:44:18 -0700	[thread overview]
Message-ID: <3D94B512.2BDF1840@digeo.com> (raw)
In-Reply-To: 20020927150249.B27592@parcelfarce.linux.theplanet.co.uk

Matthew Wilcox wrote:
> 
> At startup, tiobench does a large number of open(O_CREAT) calls, all
> in the same directory.  This leads to a large number of processes all
> trying to do down() on the parent directory's i_sem.  That wouldn't be
> so bad, but each one is sleeping with an entire page (of ZONE_NORMAL)
> allocated.  800MB of ZONE_NORMAL / 4k pages.. ok, it'd take 200,000
> tasks to completely OOM your box, but a user can certainly make life
> difficult for us with fewer tasks.
> 
> The most important question is: Do we care?  tiobench is only a benchmark.

If the fs was mounted -o sync or -o dirsync, those creates would involve
synchronous I/O inside i_sem.  So the problem is potentially more serious
in such a setup.

Even then, do we care?  Well hrm.  One page of ZONE_NORMAL per process
doesn't sound like the end of the world...

  reply	other threads:[~2002-09-27 19:44 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2002-09-27 14:02 simultaneous creates in a directory Matthew Wilcox
2002-09-27 19:44 ` Andrew Morton [this message]
2002-09-27 20:44   ` William Lee Irwin III
2002-09-27 21:08     ` Andrew Morton

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