Am Thu, 08 Apr 2010 10:05:09 +0400 schrieb Michael Tokarev: > 08.04.2010 09:07, Thomas Mueller wrote: [] >> This helped alot: >> >> I enabled "deadline" block scheduler instead of the default "cfq" on >> the host system. tested with: Host Debian with scheduler deadline, >> Guest Win2008 with Virtio and cache=none. (26MB/s to 50MB/s boost >> measured) Maybe this is also true for Linux/Linux. >> >> I expect that scheduler "noop" for linux guests would be good. > > Hmm. I wonder why it helped. In theory, host scheduler should not > change anything for cache=none case, at least for raw partitions of LVM > volumes. This is because with cache=none, the virtual disk image is > opened with O_DIRECT flag, which means all I/O bypasses host scheduler > and buffer cache. > > I tried a few quick tests here, -- with LVM volumes it makes no > measurable difference. But if the guest disk images are on plain files > (also raw), scheduler makes some difference, and indeed deadline works > better. Maybe you were testing with plain files instead of block > devices? ah yes, qcow2 images. - Thomas -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
