>From: Shirley Ma [mailto:mashirle@xxxxxxxxxx] >Sent: Wednesday, September 15, 2010 10:41 AM >To: Xin, Xiaohui >Cc: Avi Kivity; David Miller; arnd@xxxxxxxx; mst@xxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; >kvm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx >Subject: RE: [RFC PATCH 2/2] macvtap: TX zero copy between guest and host kernel > >On Wed, 2010-09-15 at 09:50 +0800, Xin, Xiaohui wrote: >> I think what David said is what we have thought before in mp device. >> Since we are not sure the exact time the tx buffer was wrote though >> DMA operation. >> But the deadline is when the tx buffer was freed. So we only notify >> the vhost stuff >> about the write when tx buffer freed. But the deadline is maybe too >> late for performance. > >Have you tried it? If so what's the performance penalty you have seen by >notifying vhost when tx buffer freed? > We did not try it before, as we cared RX side more. >I am thinking to have a callback in skb destructor, >vhost_add_used_and_signal gets updated when skb is actually freed, vhost >vq & head need to be passed to the callback. This might requires vhost >ring size is at least as big as the lower device driver. > That's almost the same what we have done except we use destructor_arg and another callback.. >Thanks >Shirley -- 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
