On 03/08/2010 06:28 PM, Anthony Liguori wrote:
I thought there was some autodetection involved, but perhaps I just
imagined it.
There's no autodetection.
linux-aio support in the kernel downgrades to synchronous IO if the
underlying storage does not support linux-aio. There is no indication
to userspace that this has happened.
If this happens, besides having a slow guest, the guest VCPU will be
starved during the I/O requests potentially resulting in things like
soft lockups and time drift.
Generally, speaking, linux-aio will work well under the following
circumstances:
- cache=off is specified
- the underlying file system is XFS or you are using a block device
We cannot detect this reliably though so it's really up to the user to
decide whether to use it. We're working on improving the linux-aio
kernel interface though to eliminate this detectability problem after
which, we can enable it in a more automatic fashion.
Well, the common case of cache=none on a block device certainly can be
autodetected.
--
error compiling committee.c: too many arguments to function
--
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
