4.15-stable review patch. If anyone has any objections, please let me know.
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From: Toshiaki Makita makita.toshiaki@lab.ntt.co.jp
[ Upstream commit fdaa767aefc1685f9a41e91f447c9aea94103df6 ]
Since commit 39e6c8208d7b ("net: solve a NAPI race") napi has been able to be rescheduled within napi_complete_done() even in non-busypoll case, but virtnet_poll() always enabled interrupts before complete, and when napi was rescheduled within napi_complete_done() it did not disable interrupts. This caused more interrupts when event idx is disabled.
According to commit cbdadbbf0c79 ("virtio_net: fix race in RX VQ processing") we cannot place virtqueue_enable_cb_prepare() after NAPI_STATE_SCHED is cleared, so disable interrupts again if napi_complete_done() returned false.
Tested with vhost-user of OVS 2.7 on host, which does not have the event idx feature.
* Before patch:
$ netperf -t UDP_STREAM -H 192.168.150.253 -l 60 -- -m 1472 MIGRATED UDP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.150.253 () port 0 AF_INET Socket Message Elapsed Messages Size Size Time Okay Errors Throughput bytes bytes secs # # 10^6bits/sec
212992 1472 60.00 32763206 0 6430.32 212992 60.00 23384299 4589.56
Interrupts on guest: 9872369 Packets/interrupt: 2.37
* After patch
$ netperf -t UDP_STREAM -H 192.168.150.253 -l 60 -- -m 1472 MIGRATED UDP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.150.253 () port 0 AF_INET Socket Message Elapsed Messages Size Size Time Okay Errors Throughput bytes bytes secs # # 10^6bits/sec
212992 1472 60.00 32794646 0 6436.49 212992 60.00 32793501 6436.27
Interrupts on guest: 4941299 Packets/interrupt: 6.64
Signed-off-by: Toshiaki Makita makita.toshiaki@lab.ntt.co.jp Acked-by: Michael S. Tsirkin mst@redhat.com Acked-by: Jason Wang jasowang@redhat.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/virtio_net.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
--- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -261,9 +261,12 @@ static void virtqueue_napi_complete(stru int opaque;
opaque = virtqueue_enable_cb_prepare(vq); - if (napi_complete_done(napi, processed) && - unlikely(virtqueue_poll(vq, opaque))) - virtqueue_napi_schedule(napi, vq); + if (napi_complete_done(napi, processed)) { + if (unlikely(virtqueue_poll(vq, opaque))) + virtqueue_napi_schedule(napi, vq); + } else { + virtqueue_disable_cb(vq); + } }
static void skb_xmit_done(struct virtqueue *vq)