Re: [Xen-users] Xen hard-disk performance regression?

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Mon, Apr 12, 2010 at 10:47:59AM +0200, Fabiano Francesconi wrote:
> On Mon, Apr 12, 2010 at 01:41:19AM +0200, Olivier B. wrote:
> > On 12/04/2010 01:29, Fabiano Francesconi wrote:
> > > I've tried with a (almost) vanilla kernel (only gentoo patchsets).
> > >
> > > I have the same issue so, I guess, it's a kernel misconfiguration /
> > > kernel regression but it must be something wrong upstream too.
> > >
> > > Since I've been sharing with you my whole anamnesi, any of you has any
> > > clue?
> > >    
> > 
> > Can you try some more synthetics tests, with "dd" ?|
> > latency on writes : dd oflag=dsync if=/dev/zero of=TESTFILE bs=4k 
> > count=10000
> > write speed :|| dd conv=fdatasync if=/dev/zero of=TESTFILE bs=4k 
> > count=128000
> > read speed : ||dd if=/dev/sda of=/dev/null bs=4k count=128000||| (this 
> > one will be greatly affected by cache)
> > 
> > And can you try with differents FS, ext3 and ext4 for example ?
> > 
> > Olivier
> 
> 
> I've ran the test you pointed me out. The results are interesting
> althought I haven't found an explanation for such a behaviour.
> 
> The dsync transfer ration is more than a minute slower on .32 kernel.
> The same for fdatasync.
> 
> This for what concerns the root hard-disk (that's *not* the one I've
> been talking since now).
> 
> The storage hard-drive, instead, shows that dsync transfer is _very_
> faster on .32, but fdatasync isn't.
> 
> These results are very strange.
> 
> You'll find both log file attached here. I made them in a way you can
> easily (vim)diff those.
> 

How about oflag=direct transfers with dd? 

Are both kernels based on the novell/sles/opensuse patches? 

-- Pasi


> -- 
> Fabiano Francesconi [GPG key: 0x81E53461]

> 2.6.29-xen-r4:
> 
> -- (guest's root partition, ext3, another hard-drive) --
> 
> $ time dd oflag=dsync if=/dev/zero of=TESTFILE bs=4k count=10000
> 
> 10000+0 records in
> 10000+0 records out
> 40960000 bytes (41 MB) copied, 477,071 s, 85,9 kB/s
> 
> real  7m57.077s
> user  0m0.004s
> sys   0m0.130s
> 
> $ time dd conv=fdatasync if=/dev/zero of=TESTFILE bs=4k count=128000 
> 128000+0 records in
> 128000+0 records out
> 524288000 bytes (524 MB) copied, 28,7759 s, 18,2 MB/s
> 
> real  0m28.782s
> user  0m0.190s
> sys   0m4.361s
> 
> $ time dd if=/dev/xvda1 of=/dev/null bs=4k count=128000
> 128000+0 records in
> 128000+0 records out
> 524288000 bytes (524 MB) copied, 11,943 s, 43,9 MB/s
> 
> real  0m11.951s
> user  0m0.014s
> sys   0m0.329s
> 
> **************************************************************************
> -- (storage hard drive, the one fully formatted with XFS) --
> 
> $ time dd oflag=dsync if=/dev/zero of=TESTFILE bs=4k count=10000
> 10000+0 records in
> 10000+0 records out
> 40960000 bytes (41 MB) copied, 431,506 s, 94,9 kB/s
> 
> real  7m11.548s
> user  0m0.002s
> sys   0m0.274s
> 
> $ time dd conv=fdatasync if=/dev/zero of=TESTFILE bs=4k count=128000
> 128000+0 records in
> 128000+0 records out
> 524288000 bytes (524 MB) copied, 21,6901 s, 24,2 MB/s
> 
> real  0m21.697s
> user  0m0.186s
> sys   0m3.140s
> 
> $ time dd if=/dev/xvdb of=/dev/null bs=4k count=128000
> 128000+0 records in
> 128000+0 records out
> 524288000 bytes (524 MB) copied, 4,884 s, 107 MB/s
> 
> real  0m4.934s
> user  0m0.059s
> sys   0m0.650s
> 

> 2.6.32-xen-r1:
> 
> -- (guest's root partition, ext3, another hard-drive) --
> $ time dd oflag=dsync if=/dev/zero of=TESTFILE bs=4k count=10000
> 10000+0 records in
> 10000+0 records out
> 40960000 bytes (41 MB) copied, 550,039 s, 74,5 kB/s
> 
> real  9m10.046s
> user  0m0.005s
> sys   0m0.133s
> 
> $ time dd conv=fdatasync if=/dev/zero of=TESTFILE bs=4k count=128000 
> 128000+0 records in
> 128000+0 records out
> 524288000 bytes (524 MB) copied, 41,5227 s, 12,6 MB/s
> 
> real  0m41.544s
> user  0m0.177s
> sys   0m2.993s
> 
> $ time dd if=/dev/xvda1 of=/dev/null bs=4k count=128000
> 128000+0 records in
> 128000+0 records out
> 524288000 bytes (524 MB) copied, 12,1582 s, 43,1 MB/s
> 
> real  0m12.165s
> user  0m0.024s
> sys   0m0.241s
> 
> **************************************************************************
> -- (storage hard drive, the one fully formatted with XFS) --
> 
> $ time dd oflag=dsync if=/dev/zero of=TESTFILE bs=4k count=10000
> 10000+0 records in
> 10000+0 records out
> 40960000 bytes (41 MB) copied, 302,612 s, 135 kB/s
> 
> real  5m2.619s
> user  0m0.003s
> sys   0m0.117s
> 
> $ time dd conv=fdatasync if=/dev/zero of=TESTFILE bs=4k count=128000
> 128000+0 records in
> 128000+0 records out
> 524288000 bytes (524 MB) copied, 30,9351 s, 16,9 MB/s
> 
> real  0m30.973s
> user  0m0.159s
> sys   0m2.274s
> 
> $ time dd if=/dev/xvdb of=/dev/null bs=4k count=128000
> 128000+0 records in
> 128000+0 records out
> 524288000 bytes (524 MB) copied, 4,80787 s, 109 MB/s
> 
> real  0m4.993s
> user  0m0.042s
> sys   0m0.509s

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