On Tue, Sep 14, 2010 at 11:49:03AM -0700, Shirley Ma wrote: > On Tue, 2010-09-14 at 20:27 +0200, Michael S. Tsirkin wrote: > > As others said, the harder issues for TX are in determining that it's > > safe > > to unpin the memory, and how much memory is it safe to pin to beging > > with. For RX we have some more complexity. > > I think unpin the memory is in kfree_skb() whenever the last reference > is gone for TX. What we discussed about here is when/how vhost get > notified to update ring buffer descriptors. Do I misunderstand something > here? Right, that's a better way to put it. > > Well it's up to you of course, but this is not what I would try: > > if you look at the > > patchset vhost changes is not the largest part of it, > > so this sounds a bit like effort duplication. > > > > TX only is also much less interesting than full zero copy. > > It's not true. From the performance, TX only has gained big improvement. > We need to identify how much gain from TX zero copy, and how much gain > from RX zero copy. I was speaking from the code point of view: since we'll want both TX and RX eventually it's nice to see that some thought was given to RX even if we only merge TX as a first step. >From the product POV, RX is already slower (more interrupts, etc) than TX so speeding it up might be more important, but I agree, every bit helps. > > I think that you should be able to simply combine > > the two drivers together, add an ioctl to > > enable/disable zero copy mode of operation. > > That could work. But what's the purpose to have two drivers if one > driver can handle it? > > Thanks > Shirley This was just an idea: I thought it's a good way for people interested in this zero copy thing to combine forces and avoid making the same mistakes, but it's not a must of course. -- 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
