linux-ext4 - Re: Bad ext4 sync performance on 16 TB GPT partition

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Date:	Mon, 1 Mar 2010 09:57:31 +0100 (CET)
From:	Karsten Weiss <K.Weiss@...ence-computing.de>
To:	Eric Sandeen <sandeen@...hat.com>
cc:	Dmitry Monakhov <dmonakhov@...nvz.org>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: Re: Bad ext4 sync performance on 16 TB GPT partition

Hi Eric,

On Fri, 26 Feb 2010, Eric Sandeen wrote:

> > => The problem shows only with the CentOS / Red Hat 5.4 kernels (including 
> > RH's test kernel 2.6.18-190.el5). Aadmittedly ext4 is only a technology 
> > preview in 5.4...
> > 
> > I've also tried the latest CentOS 5.3 kernel-2.6.18-128.7.1.el5 but 
> > couldn't mount the device (with -t ext4dev).
> > 
> > 2.6.18-164.el5 (the initial CentOS 5.4 kernel) has the bug, too.
> > 
> > I'm willing to test patches if somebody wants to debug the problem.
> 
> Ok, that's interesting.  We've not had bona-fide RHEL customers report
> the problem, but then maybe it hasn't been tested this way.

I think so because, as I mentioned, the issue can be reproduced with the 
RH test kernel 2.6.18-190.el5 x86_64 (http://people.redhat.com/jwilson/el5/),
too.

> 2.6.18-178.el5 and beyond is based on the 2.6.32 codebase for ext4.
> 
> Testing generic 2.6.32 might also be interesting as a datapoint,
> if you're willing.

Sorry for the delay, here's the (good) 2.6.32 result:

# /usr/bin/time bash -c "dd if=/dev/zero of=/mnt/large/10GB bs=1M count=10000 && sync"
10000+0 records in
10000+0 records out
10485760000 bytes (10 GB) copied, 46.3369 seconds, 226 MB/s
0.00user 14.17system 0:59.53elapsed 23%CPU (0avgtext+0avgdata 6224maxresident)k
0inputs+0outputs (0major+1045minor)pagefaults 0swaps

To summarize:

Bad:  2.6.18-164.el5 (CentOS)
Bad:  2.6.18-164.11.1el5 (CentOS)
Bad:  2.6.18-190.el5 (RH)
Good: 2.6.32
Good: 2.6.33

-- 
Karsten Weiss
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