On 08/17/2011 09:38 PM, Sasha Levin wrote:
On Wed, 2011-08-17 at 16:00 -0700, Avi Kivity wrote: > On 08/16/2011 12:47 PM, Sasha Levin wrote: > > This patch adds support for an optional stats vq that works similary to the > > stats vq provided by virtio-balloon. > > > > The purpose of this change is to allow collection of statistics about working > > virtio-blk devices to easily analyze performance without having to tap into > > the guest. > > > > > > Why can't you get the same info from the host? i.e. read sectors? Some of the stats you can collect from the host, but some you can't. The ones you can't include all the timing statistics and the internal queue statistics (read/write merges).
Surely you can time the actual amount of time the I/O takes? It doesn't account for the virtio round-trip, but does it matter?
Why is the merge count important for the host?
The idea behind providing all of the stats on the stats vq (which is basically what you see in '/dev/block/[device]/stats') is to give a consistent snapshot of the state of the device.
What can you do with it? -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain. -- 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
