On Wed, 9 Feb 2011 11:23:45 am Michael S. Tsirkin wrote: > On Wed, Feb 09, 2011 at 11:07:20AM +1030, Rusty Russell wrote: > > On Wed, 2 Feb 2011 03:12:22 pm Michael S. Tsirkin wrote: > > > On Wed, Feb 02, 2011 at 10:09:18AM +0530, Krishna Kumar2 wrote: > > > > > "Michael S. Tsirkin" <mst@xxxxxxxxxx> 02/02/2011 03:11 AM > > > > > > > > > > On Tue, Feb 01, 2011 at 01:28:45PM -0800, Shirley Ma wrote: > > > > > > On Tue, 2011-02-01 at 23:21 +0200, Michael S. Tsirkin wrote: > > > > > > > Confused. We compare capacity to skb frags, no? > > > > > > > That's sg I think ... > > > > > > > > > > > > Current guest kernel use indirect buffers, num_free returns how many > > > > > > available descriptors not skb frags. So it's wrong here. > > > > > > > > > > > > Shirley > > > > > > > > > > I see. Good point. In other words when we complete the buffer > > > > > it was indirect, but when we add a new one we > > > > > can not allocate indirect so we consume. > > > > > And then we start the queue and add will fail. > > > > > I guess we need some kind of API to figure out > > > > > whether the buf we complete was indirect? > > > > I've finally read this thread... I think we need to get more serious > > with our stats gathering to diagnose these kind of performance issues. > > > > This is a start; it should tell us what is actually happening to the > > virtio ring(s) without significant performance impact... > > > > Subject: virtio: CONFIG_VIRTIO_STATS > > > > For performance problems we'd like to know exactly what the ring looks > > like. This patch adds stats indexed by how-full-ring-is; we could extend > > it to also record them by how-used-ring-is if we need. > > > > Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx> > > Not sure whether the intent is to merge this. If yes - > would it make sense to use tracing for this instead? > That's what kvm does. Intent wasn't; I've not used tracepoints before, but maybe we should consider a longer-term monitoring solution? Patch welcome! Cheers, Rusty. -- 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
