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Re: Extreme slowness with xfs [WAS: Re: Slowness with new pc]

To: Eric Sandeen <sandeen@xxxxxxxxxxx>
Subject: Re: Extreme slowness with xfs [WAS: Re: Slowness with new pc]
From: Justin Piszcz <jpiszcz@xxxxxxxxxxxxxxx>
Date: Tue, 25 Nov 2008 04:56:24 -0500 (EST)
Cc: Stian Jordet <liste@xxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx, Alan Piszcz <ap@xxxxxxxxxxxxx>
In-reply-to: <492B5684.2080107@xxxxxxxxxxx>
References: <1226760254.5089.11.camel@chevrolet> <430c4fa50811180551r67d5d680tf1ffa493604ac4ea@xxxxxxxxxxxxxx> <1227476908.32357.5.camel@chevrolet> <alpine.DEB.1.10.0811231721350.22594@xxxxxxxxxxxxxxxx> <1227485956.5145.10.camel@chevrolet> <alpine.DEB.1.10.0811240448570.25866@xxxxxxxxxxxxxxxx> <1227569808.5039.6.camel@chevrolet> <492B5684.2080107@xxxxxxxxxxx>
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On Mon, 24 Nov 2008, Eric Sandeen wrote:

Stian Jordet wrote:
ma., 24.11.2008 kl. 04.50 -0500, skrev Justin Piszcz:
While there still may be something else wrong, the first problem I see is
your sunit and swidth are set to 0.

Please read, a good article on what they are and how to set them:
http://www.socalsysadmin.com/

Oh, this was new to me. But the setting didn't change anything. I can
copy one large file between the xfs and ext3 disk (both ways), and I get
speeds between 160 and 200 MB/s. But unpacking the kernel source takes
between 5 and 10 minutes on the xfs disk, and a mere 15 seconds on the
ext3... (and it also used to take between 5 and 10 minutes when I had
xfs on the raid0, so it doesn't seem to be hardware related...)

If anyone has anything more I can try before I do the lengthy process of
backup 1TB, reformat and restore...

I don't know if the storage you're on passes barriers or not, but xfs
has barriers on by default, while ext3 does not.  ext3 will still likely
win the "untar a kernel" race, but for a fairer test, make the barrier
settings consistent between the two.

-Eric


barriers enabled:

$ time bash -c 'tar xf linux-2.6.27.7.tar; sync'
block 573932: ** Block of NULs **
Total bytes read: 293857280 (281MiB, 1.9MiB/s)

real    2m40.643s
user    0m0.194s
sys     0m1.541s

barriers disabled:

time bash -c 'tar xf linux-2.6.27.7.tar; sync'
block 573932: ** Block of NULs **
Total bytes read: 293857280 (281MiB, 11MiB/s)

real    0m27.612s
user    0m0.182s
sys     0m1.617s


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