On Tue, Sep 14, 2010 at 07:40:52PM -0700, Shirley Ma wrote: > 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? > > 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. > > Thanks > Shirley For some of the issues, try following the discussion around net: af_packet: don't call tpacket_destruct_skb() until the skb is sent out. Summary: it's difficult to do correctly generally. Limiting ourselves to transmit on specific devices might make it possible. -- MST -- 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
