On Mon, Mar 22, 2010 at 05:34:04PM -0700, Badari Pulavarty wrote: > Write Results: > ============== > > I see degraded IO performance when doing sequential IO write > tests with vhost-blk compared to virtio-blk. > > # time dd of=/dev/vda if=/dev/zero bs=2M oflag=direct > > I get ~110MB/sec with virtio-blk, but I get only ~60MB/sec with > vhost-blk. Wondering why ?
Try to look and number of interrupts and/or number of exits. It could also be that you are overrunning some queue. I don't see any exit mitigation strategy in your patch: when there are already lots of requests in a queue, it's usually a good idea to disable notifications and poll the queue as requests complete. That could help performance. -- MST
