在 2021/4/13 上午11:15, Xuan Zhuo 写道:
After testing, the performance of calling kick every time is not stable.
And if all the packets are sent and kicked again, the performance is not
good. So add a module parameter to specify how many packets are sent to
call a kick.
8 is a relatively stable value with the best performance.
Here is the pps of the test of xsk_kick_thr under different values (from
1 to 64).
thr PPS thr PPS thr PPS
1 2924116.74247 | 23 3683263.04348 | 45 2777907.22963
2 3441010.57191 | 24 3078880.13043 | 46 2781376.21739
3 3636728.72378 | 25 2859219.57656 | 47 2777271.91304
4 3637518.61468 | 26 2851557.9593 | 48 2800320.56575
5 3651738.16251 | 27 2834783.54408 | 49 2813039.87599
6 3652176.69231 | 28 2847012.41472 | 50 3445143.01839
7 3665415.80602 | 29 2860633.91304 | 51 3666918.01281
8 3665045.16555 | 30 2857903.5786 | 52 3059929.2709
9 3671023.2401 | 31 2835589.98963 | 53 2831515.21739
10 3669532.23274 | 32 2862827.88706 | 54 3451804.07204
11 3666160.37749 | 33 2871855.96696 | 55 3654975.92385
12 3674951.44813 | 34 3434456.44816 | 56 3676198.3188
13 3667447.57331 | 35 3656918.54177 | 57 3684740.85619
14 3018846.0503 | 36 3596921.16722 | 58 3060958.8594
15 2792773.84505 | 37 3603460.63903 | 59 2828874.57191
16 3430596.3602 | 38 3595410.87666 | 60 3459926.11027
17 3660525.85806 | 39 3604250.17819 | 61 3685444.47599
18 3045627.69054 | 40 3596542.28428 | 62 3049959.0809
19 2841542.94177 | 41 3600705.16054 | 63 2806280.04013
20 2830475.97348 | 42 3019833.71191 | 64 3448494.3913
21 2845655.55789 | 43 2752951.93264 |
22 3450389.84365 | 44 2753107.27164 |
It can be found that when the value of xsk_kick_thr is relatively small,
the performance is not good, and when its value is greater than 13, the
performance will be more irregular and unstable. It looks similar from 3
to 13, I chose 8 as the default value.
The test environment is qemu + vhost-net. I modified vhost-net to drop
the packets sent by vm directly, so that the cpu of vm can run higher.
By default, the processes in the vm and the cpu of softirqd are too low,
and there is no obvious difference in the test data.
During the test, the cpu of softirq reached 100%. Each xsk_kick_thr was
run for 300s, the pps of every second was recorded, and the average of
the pps was finally taken. The vhost process cpu on the host has also
reached 100%.
Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
Reviewed-by: Dust Li <dust.li@xxxxxxxxxxxxxxxxx>
---
drivers/net/virtio_net.c | 19 +++++++++++++++++--
1 file changed, 17 insertions(+), 2 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index c441d6bf1510..4e360bfc2cf0 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -28,9 +28,11 @@ static int napi_weight = NAPI_POLL_WEIGHT;
module_param(napi_weight, int, 0444);
static bool csum = true, gso = true, napi_tx = true;
+static int xsk_kick_thr = 8;
module_param(csum, bool, 0444);
module_param(gso, bool, 0444);
module_param(napi_tx, bool, 0644);
+module_param(xsk_kick_thr, int, 0644);
/* FIXME: MTU in config. */
#define GOOD_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN)
@@ -2690,6 +2692,7 @@ static int virtnet_xsk_xmit_batch(struct send_queue *sq,
struct xdp_desc desc;
int err, packet = 0;
int ret = -EAGAIN;
+ int need_kick = 0;
if (sq->xsk.last_desc.addr) {
if (sq->vq->num_free < 2 + MAX_SKB_FRAGS)
@@ -2700,6 +2703,7 @@ static int virtnet_xsk_xmit_batch(struct send_queue *sq,
return -EBUSY;
++packet;
+ ++need_kick;
--budget;
sq->xsk.last_desc.addr = 0;
}
@@ -2723,11 +2727,22 @@ static int virtnet_xsk_xmit_batch(struct send_queue *sq,
}
++packet;
+ ++need_kick;
+ if (need_kick > xsk_kick_thr) {
+ if (virtqueue_kick_prepare(sq->vq) &&
+ virtqueue_notify(sq->vq))
I woner whether it's time to introduce a helper in the virtio core to do
this.
Thanks
+ ++stats->kicks;
+
+ need_kick = 0;
+ }
}
if (packet) {
- if (virtqueue_kick_prepare(sq->vq) && virtqueue_notify(sq->vq))
- ++stats->kicks;
+ if (need_kick) {
+ if (virtqueue_kick_prepare(sq->vq) &&
+ virtqueue_notify(sq->vq))
+ ++stats->kicks;
+ }
*done = packet;
stats->xdp_tx += packet;
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