linux-kernel - Re: Poor interactive performance with I/O loads with fsync()ing

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Date:	Mon, 12 Apr 2010 10:22:25 +1000
From:	Dave Chinner <david@...morbit.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Avi Kivity <avi@...hat.com>, Ben Gamari <bgamari.foss@...il.com>,
	Andi Kleen <andi@...stfloor.org>,
	Arjan van de Ven <arjan@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>, tytso@....edu,
	npiggin@...e.de, Ingo Molnar <mingo@...e.hu>,
	Ruald Andreae <ruald.a@...il.com>,
	Jens Axboe <jens.axboe@...cle.com>,
	Olly Betts <olly@...vex.com>,
	martin f krafft <madduck@...duck.net>
Subject: Re: Poor interactive performance with I/O loads with fsync()ing

On Sun, Apr 11, 2010 at 08:16:09PM +0200, Thomas Gleixner wrote:
> On Sun, 11 Apr 2010, Avi Kivity wrote:
> > On 04/09/2010 05:56 PM, Ben Gamari wrote:
> > > On Mon, 29 Mar 2010 00:08:58 +0200, Andi Kleen<andi@...stfloor.org>  wrote:
> > > > Ben Gamari<bgamari.foss@...il.com>  writes:
> > > > ext4/XFS/JFS/btrfs should be better in this regard
> > > > 
> > > I am using btrfs, so yes, I was expecting things to be better.
> > > Unfortunately,
> > > the improvement seems to be non-existent under high IO/fsync load.
> > 
> > btrfs is known to perform poorly under fsync.
> 
> XFS does not do much better. Just moved my VM images back to ext for
> that reason.

Numbers? Workload description? Mount options? I hate it when all I
hear is "XFS sucked, so I went back to extN" reports without any
more details - it's hard to improve anything without any details
of the problems.

Also worth remembering is that XFS defaults to slow-but-safe
options, but ext3 defaults to fast-and-I-don't-give-a-damn-about-
data-safety, so there's a world of difference between the
filesystem defaults....

And FWIW, I run all my VMs on XFS using default mkfs and mount options,
and I can't say that I've noticed any performance problems at all
despite hammering the IO subsystems all the time. The only thing
I've ever done is occasionally run xfs_fsr across permanent qcow2
VM images to defrag them as the grow slowly over time...

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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