On Wed, 2011-05-18 at 00:58 +0200, MichaÅ MirosÅaw wrote: > W dniu 18 maja 2011 00:28 uÅytkownik Shirley Ma <mashirle@xxxxxxxxxx> > napisaÅ: > > On Tue, 2011-05-17 at 23:48 +0200, MichaÅ MirosÅaw wrote: > >> 2011/5/17 Shirley Ma <mashirle@xxxxxxxxxx>: > >> > Looks like to use a new flag requires more time/work. I am > thinking > >> > whether we can just use HIGHDMA flag to enable zero-copy in > macvtap > >> to > >> > avoid the new flag for now since mavctap uses real NICs as lower > >> device? > >> > >> Is there any other restriction besides requiring driver to not > recycle > >> the skb? Are there any drivers that recycle TX skbs? > > Not more other restrictions, skb clone is OK. pskb_expand_head() > looks > > OK to me from code review. > > > Currently there is no drivers recycle TX skbs. > > So why do you require the target device to have some flags at all? We could use macvtap to check lower device HIGHDMA to enable zero-copy, but I am not sure whether it is sufficient. If it's sufficient then we don't need to use a new flag here. To be safe, it's better to use a new flag to enable each device who can pass zero-copy test. > Do I understand correctly, that this zero-copy feature is about > packets received from VMs? Yes, packets sent from VMs, and received in local host for TX zero-copy here. 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
