On Thu, Dec 06, 2012 at 08:03:14PM +0000, Ben Hutchings wrote: > On Thu, 2012-12-06 at 10:13 +0200, Michael S. Tsirkin wrote: > > On Wed, Dec 05, 2012 at 08:39:26PM +0000, Ben Hutchings wrote: > > > On Mon, 2012-12-03 at 12:58 +0200, Michael S. Tsirkin wrote: > > > > Add RFS support to virtio network device. > > > > Add a new feature flag VIRTIO_NET_F_RFS for this feature, a new > > > > configuration field max_virtqueue_pairs to detect supported number of > > > > virtqueues as well as a new command VIRTIO_NET_CTRL_RFS to program > > > > packet steering for unidirectional protocols. > > > [...] > > > > +Programming of the receive flow classificator is implicit. > > > > + Transmitting a packet of a specific flow on transmitqX will cause incoming > > > > + packets for this flow to be steered to receiveqX. > > > > + For uni-directional protocols, or where no packets have been transmitted > > > > + yet, device will steer a packet to a random queue out of the specified > > > > + receiveq0..receiveqn. > > > [...] > > > > > > It doesn't seem like this is usable to implement accelerated RFS in the > > > guest, though perhaps that doesn't matter. > > > > What is the issue? Could you be more explicit please? > > > > It seems to work pretty well: if we have > > # of queues >= # of cpus, incoming TCP_STREAM into > > guest scales very nicely without manual tweaks in guest. > > > > The way it works is, when guest sends a packet driver > > select the rx queue that we want to use for incoming > > packets for this slow, and transmit on the matching tx queue. > > This is exactly what text above suggests no? > > Yes, I get that. > > > > On the host side, presumably > > > you'll want vhost_net to do the equivalent of sock_rps_record_flow() - > > > only without a socket? But in any case, that requires an rxhash, so I > > > don't see how this is supposed to work. > > > > > > Ben. > > > > Host should just do what guest tells it to. > > On the host side we build up the steering table as we get packets > > to transmit. See the code in drivers/net/tun.c in recent > > kernels. > > > > Again this actually works fine - what are the problems that you see? > > Could you give an example please? > > I'm not saying it doesn't work in its own way, I just don't see how you > would make it work with the existing RFS! > > Since this doesn't seem to be intended to have *any* connection with the > existing core networking feature called RFS, perhaps you could find a > different name for it. > > Ben. Ah I see what you mean. We started out calling this feature "multiqueue" Rusty suggested "RFS" since it gives similar functionality to RFS but in device: it has receive steering logic per flow as part of the device. Maybe simply adding a statement similar to the one above would be sufficient to avoid confusion? > -- > Ben Hutchings, Staff Engineer, Solarflare > Not speaking for my employer; that's the marketing department's job. > They asked us to note that Solarflare product names are trademarked. -- 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
