Re: [PATCH RFC] virtio: put last seen used index into ring itself

2010-05-11 Thread Ryan Harper
* Michael S. Tsirkin m...@redhat.com [2010-05-05 16:37]: Generally, the Host end of the virtio ring doesn't need to see where Guest is up to in consuming the ring. However, to completely understand what's going on from the outside, this information must be exposed. For example, host can

Re: [PATCH RFC] virtio: put last seen used index into ring itself

2010-05-11 Thread Michael S. Tsirkin
On Tue, May 11, 2010 at 01:46:08PM -0500, Ryan Harper wrote: * Michael S. Tsirkin m...@redhat.com [2010-05-05 16:37]: Generally, the Host end of the virtio ring doesn't need to see where Guest is up to in consuming the ring. However, to completely understand what's going on from the

Re: [PATCH RFC] virtio: put last seen used index into ring itself

2010-05-06 Thread Rusty Russell
On Thu, 6 May 2010 03:49:46 pm Michael S. Tsirkin wrote: Now, I also added an mb() in guest between read and write so that last used index write can not get ahead of used index read. It does feel good to have it there, but I can not say why it's helpful. Works fine without it, but then these

Re: [PATCH RFC] virtio: put last seen used index into ring itself

2010-05-05 Thread Dor Laor
On 05/05/2010 11:58 PM, Michael S. Tsirkin wrote: Generally, the Host end of the virtio ring doesn't need to see where Guest is up to in consuming the ring. However, to completely understand what's going on from the outside, this information must be exposed. For example, host can reduce the

Re: [PATCH RFC] virtio: put last seen used index into ring itself

2010-05-05 Thread Rusty Russell
On Thu, 6 May 2010 06:28:14 am Michael S. Tsirkin wrote: Rusty, this is a simplified form of a patch you posted in the past. I have a vhost patch that, using this feature, shows external to host bandwidth grow from 5 to 7 GB/s, by avoiding an interrupt in the window after previous interrupt