[OmniOS-discuss] kvm io 10 times slower after r151010 -> r151012 upgrade

[Tobias Oetiker]

Hi Michael,

so your tests wer now exectued on a bloody host ?

indicating that the performance went back up in bloody ?

cheers
tobi

Today Michael Mounteney wrote:

> Sorry to take so long to get back to you Tobias and I hope this is
> still relevant.  As described elsewhere in this list, I had temporarily
> to downgrade ssh to achieve interoperability between the OmniOS (bloody)
> host and the Gentoo Linux guests.
>
> First, ssh imposes some overhead:
>
> mounty at pantry ~ $ time ssh people exit
>
> real	0m0.724s
> user	0m0.032s
> sys	0m0.012s
>
> that real figure averages around the 0.750s mark.  So I decided to
> perform much bigger transfers to minimise its effect:
>
> mounty at pantry ~ $ dd if=/dev/zero bs=1M count=2000 | ssh people dd of=/dev/null
> 2000+0 records in
> 2000+0 records out
> 2097152000 bytes (2.1 GB) copied, 138.436 s, 15.1 MB/s
> 4096000+0 records in
> 4096000+0 records out
> 2097152000 bytes transferred in 137.657582 secs (15234555 bytes/sec)
>
> mounty at pantry ~ $ ssh people dd if=/dev/zero bs=1M count=2000 | dd of=/dev/null
> 2000+0 records in
> 2000+0 records out
> 2097152000 bytes transferred in 51.692313 secs (40569901 bytes/sec)
> 4096000+0 records in
> 4096000+0 records out
> 2097152000 bytes (2.1 GB) copied, 52.4503 s, 40.0 MB/s
>
> It is puzzling that the in and out figures are so different but I did
> perform each test three times and the results were approximately the
> same each time.  On the read-off-disk test, here are all three runs:
>
> pantry ~ # dd if=/dev/vda of=/dev/zero bs=1M count=1000
> 1000+0 records in
> 1000+0 records out
> 1048576000 bytes (1.0 GB) copied, 65.3406 s, 16.0 MB/s
> pantry ~ # dd if=/dev/vda of=/dev/zero bs=1M count=1000
> 1000+0 records in
> 1000+0 records out
> 1048576000 bytes (1.0 GB) copied, 1.19789 s, 875 MB/s
> pantry ~ # dd if=/dev/vda of=/dev/zero bs=1M count=1000
> 1000+0 records in
> 1000+0 records out
> 1048576000 bytes (1.0 GB) copied, 1.85877 s, 564 MB/s
>
> which I've quoted to show that the disk must be cached.  So I tried
> again with more data to eliminate that effect:
>
> pantry ~ # dd if=/dev/vda of=/dev/zero bs=1M count=10240
> 10240+0 records in
> 10240+0 records out
> 10737418240 bytes (11 GB) copied, 710.215 s, 15.1 MB/s
>
> I hope that's helpful.
>
> Michael.
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>
>

-- 
Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten, Switzerland
www.oetiker.ch tobi at oetiker.ch +41 62 775 9902