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Date: Tue, 24 Mar 2009 16:03:53 -0700
From: Jesse Barnes <jbarnes@virtuousgeek.org>
To: Theodore Tso <tytso@mit.edu>
Cc: Ingo Molnar <mingo@elte.hu>, Alan Cox <alan@lxorguk.ukuu.org.uk>,
       Arjan van de Ven <arjan@infradead.org>,
       Andrew Morton <akpm@linux-foundation.org>,
       Peter Zijlstra <a.p.zijlstra@chello.nl>, Nick Piggin <npiggin@suse.de>,
       Jens Axboe <jens.axboe@oracle.com>, David Rees <drees76@gmail.com>,
       Jesper Krogh <jesper@krogh.cc>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Linux 2.6.29
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On Tue, 24 Mar 2009 09:20:32 -0400
Theodore Tso <tytso@mit.edu> wrote:
> They don't solve the problem where there is a *huge* amount of writes
> going on, though --- if something is dirtying pages at a rate far
> greater than the local disk can write it out, say, either "dd
> if=/dev/zero of=/mnt/make-lots-of-writes" or a massive distcc cluster
> driving a huge amount of data towards a single system or a wget over a
> local 100 megabit ethernet from a massive NFS server where everything
> is in cache, then you can have a major delay with the fsync().

You make it sound like this is hard to do...  I was running into this
problem *every day* until I moved to XFS recently.  I'm running a
fairly beefy desktop (VMware running a crappy Windows install w/AV junk
on it, builds, icecream and large mailboxes) and have a lot of RAM, but
it became unusable for minutes at a time, which was just totally
unacceptable, thus the switch.  Things have been better since, but are
still a little choppy.

I remember early in the 2.6.x days there was a lot of focus on making
interactive performance good, and for a long time it was.  But this I/O
problem has been around for a *long* time now... What happened?  Do not
many people run into this daily?  Do all the filesystem hackers run
with special mount options to mitigate the problem?

-- 
Jesse Barnes, Intel Open Source Technology Center
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