On Sun, Apr 2, 2017 at 10:30 PM, Michael S. Tsirkin <mst@xxxxxxxxxx> wrote: > On Sun, Apr 02, 2017 at 04:10:11PM -0400, Willem de Bruijn wrote: >> From: Willem de Bruijn <willemb@xxxxxxxxxx> >> >> Convert virtio-net to a standard napi tx completion path. This enables >> better TCP pacing using TCP small queues and increases single stream >> throughput. >> >> The virtio-net driver currently cleans tx descriptors on transmission >> of new packets in ndo_start_xmit. Latency depends on new traffic, so >> is unbounded. To avoid deadlock when a socket reaches its snd limit, >> packets are orphaned on tranmission. This breaks socket backpressure, >> including TSQ. >> >> Napi increases the number of interrupts generated compared to the >> current model, which keeps interrupts disabled as long as the ring >> has enough free descriptors. Keep tx napi optional for now. Follow-on >> patches will reduce the interrupt cost. >> >> Signed-off-by: Willem de Bruijn <willemb@xxxxxxxxxx> >> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx> >> --- >> drivers/net/virtio_net.c | 63 ++++++++++++++++++++++++++++++++++++++++-------- >> 1 file changed, 53 insertions(+), 10 deletions(-) >> >> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c >> index 6aac0ad0d9b2..95d938e82080 100644 >> --- a/drivers/net/virtio_net.c >> +++ b/drivers/net/virtio_net.c >> @@ -33,9 +33,10 @@ >> static int napi_weight = NAPI_POLL_WEIGHT; >> module_param(napi_weight, int, 0444); >> >> -static bool csum = true, gso = true; >> +static bool csum = true, gso = true, napi_tx = true; >> module_param(csum, bool, 0444); >> module_param(gso, bool, 0444); >> +module_param(napi_tx, bool, 0644); >> >> /* FIXME: MTU in config. */ >> #define GOOD_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN) > > Off by default seems safer until we can find better ways > to reduce the overhead, esp for UDP. Okay, I'll change that. I don't have an immediate idea for that unidirectional case. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
