On Tue, 2 Jun 2009 05:43:42 pm Mark McLoughlin wrote: > On Fri, 2009-05-29 at 23:46 +0930, Rusty Russell wrote: > > The virtio_net driver is complicated by the two methods of freeing old > > xmit buffers (in addition to freeing old ones at the start of the xmit > > path). > > > > The original code used a 1/10 second timer attached to xmit_free(), > > reset on every xmit. Before we orphaned skbs on xmit, the > > transmitting userspace could block with a full socket until the timer > > fired, the skb destructor was called, and they were re-woken. > > The timer was actually added to solve a hang when trying to unload > nf_conntrack AFAIR - nf_conntrack was blocking on the skb being freed > and we never actually freed it. > > I think skb_orphan() is enough to prevent this, is it? Yep. > > Unfortunately, VIRTIO_F_NOTIFY_ON_EMPTY makes quite a lot of work: a > > host which is faster than the guest will fire the interrupt every xmit > > packet (slowing the guest down further). > > Ouch. So, does simply disabling host support for > VIRTIO_F_NOTIFY_ON_EMPTY speed up current guests? That was my original change. It cuts the interrupts, but there's enough else going on that there's not a reliably-measurable speedup (this is with lguest, haven't tested with kvm). Cheers, Rusty. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization
