From fdaa767aefc1685f9a41e91f447c9aea94103df6 Mon Sep 17 00:00:00 2001
From: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
Date: Thu, 7 Dec 2017 13:15:15 +0900
Subject: [PATCH] virtio_net: Disable interrupts if napi_complete_done rescheduled napi
Git-commit: fdaa767aefc1685f9a41e91f447c9aea94103df6
Patch-mainline: v4.16-rc1
References: bsc#1051510
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>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/net/virtio_net.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 19a985ef9104..c0db48de7bf9 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -261,9 +261,12 @@ static void virtqueue_napi_complete(struct napi_struct *napi,
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)
--
2.18.0