[kernel-xen] kernel-xen-3.11.0-1 in testing repo.

Steven Haigh netwiz at crc.id.au
Tue Sep 17 11:56:31 EST 2013

On 17/09/13 11:30, Glenn Enright wrote:
> Preliminary (very) testing seems to indicate a good boost (using 3.11.1)
> Seeing about a 20% increase on buffered writes, and a small but marked
> increase on syncronised writes. Which is nice. Keep in mind this is on
> an unloaded host with only a couple of VMs.
> In detail ...
> I'm working on a machine with VMs backed by lvm disk over raid1 (using
> budget sata drives), with the following snippet, with and without the
> fsync option. The test domU uses the noop scheduler.
> for i in 1 2 3 4 5
> do
>   dd if=/dev/zero of=speedtest bs=1M count=1024 conv=fsync
> done
> 3.10 domO, default behavour, custom domu kernel
> using fsync average 58 MB/s, without fsync average 59 MB/s,
> 3.11 domO, default behaviour, 3.11 kernel on domu
> using fsync average 58 MB/s (ie the same)
> 3.11 domO, using xen-blkfront.max=128, 3.11 kernel on domU
> using fsync average 62 MB/s, without fsync average 68 MB/s

This is good to see. I'd actually expect a bit more than that - but
either way, its good to see an increase in throughput. What actual
drives are these? I use Seagate 1Tb 7200rpm SATA drives in my home test
setup - but I haven't done a throughput test on the RAID1 as yet - as it
hasn't really been problematic in the past.

There is talk around this having a way to automatically do a test and
set xen-blkfront.max to an optimal value on initialisation of the DomU
blkfront module. As yet, this is only talk - however it would probably
be a good step forwards.

It may even get to the point where it could be backported into distro
kernels - and therefore not require the upgrade to 3.11 on the DomU to
take advantage of this - however that would be a job for various distros.

Steven Haigh

Email: netwiz at crc.id.au
Web: https://www.crc.id.au
Phone: (03) 9001 6090 - 0412 935 897
Fax: (03) 8338 0299

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