On 2019/8/15 下午4:36, 冉 jiang wrote:
On 2019/8/15 11:17, Jason Wang wrote:On 2019/8/15 上午11:11, 冉 jiang wrote:On 2019/8/15 11:01, Jason Wang wrote:On 2019/8/14 上午10:06, ? jiang wrote:This change lowers ring buffer reclaim threshold from 1/2*queue to budget for better performance. According to our test with qemu + dpdk, packet dropping happens when the guest is not able to provide free buffer in avail ring timely with default 1/2*queue. The value in the patch has been tested and does show better performance.Please add your tests setup and result here. ThanksSigned-off-by: jiangkidd <jiangkidd@xxxxxxxxxxx> --- drivers/net/virtio_net.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 0d4115c9e20b..bc08be7925eb 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -1331,7 +1331,7 @@ static int virtnet_receive(struct receive_queue *rq, int budget, } } - if (rq->vq->num_free > virtqueue_get_vring_size(rq->vq) / 2) { + if (rq->vq->num_free > min((unsigned int)budget, virtqueue_get_vring_size(rq->vq)) / 2) { if (!try_fill_recv(vi, rq, GFP_ATOMIC)) schedule_delayed_work(&vi->refill, 0); }Sure, here are the details:Thanks for the details, but I meant it's better if you could summarize you test result in the commit log in a compact way. Btw, some comments, see below:Test setup & result: ---------------------------------------------------- Below is the snippet from our test result. Test1 was done with default driver with the value of 1/2 * queue, while test2 is with my patch. We can see average drop packets do decrease a lot in test2. test1Time avgDropPackets test2Time avgDropPackets pps 16:21.0 12.295 56:50.4 0 300k 17:19.1 15.244 56:50.4 0 300k 18:17.5 18.789 56:50.4 0 300k 19:15.1 14.208 56:50.4 0 300k 20:13.2 20.818 56:50.4 0.267 300k 21:11.2 12.397 56:50.4 0 300k 22:09.3 12.599 56:50.4 0 300k 23:07.3 15.531 57:48.4 0 300k 24:05.5 13.664 58:46.5 0 300k 25:03.7 13.158 59:44.5 4.73 300k 26:01.1 2.486 00:42.6 0 300k 26:59.1 11.241 01:40.6 0 300k 27:57.2 20.521 02:38.6 0 300k 28:55.2 30.094 03:36.7 0 300k 29:53.3 16.828 04:34.7 0.963 300k 30:51.3 46.916 05:32.8 0 400k 31:49.3 56.214 05:32.8 0 400k 32:47.3 58.69 05:32.8 0 400k 33:45.3 61.486 05:32.8 0 400k 34:43.3 72.175 05:32.8 0.598 400k 35:41.3 56.699 05:32.8 0 400k 36:39.3 61.071 05:32.8 0 400k 37:37.3 43.355 06:30.8 0 400k 38:35.4 44.644 06:30.8 0 400k 39:33.4 72.336 06:30.8 0 400k 40:31.4 70.676 06:30.8 0 400k 41:29.4 108.009 06:30.8 0 400k 42:27.4 65.216 06:30.8 0 400kWhy there're difference in test time? Could you summarize them like: Test setup: e.g testpmd or pktgen to generate packets to guest avg packets drop before: XXX avg packets drop after: YYY(-ZZZ%) ThanksData to prove why the patch helps: ---------------------------------------------------- We did have completed several rounds of test with setting the value to budget (64 as the default value). It does improve a lot with pps is below 400pps for a single stream. We are confident that it runs out of free buffer in avail ring when packet dropping happens with below systemtap: Just a snippet: probe module("virtio_ring").function("virtqueue_get_buf") { x = (@cast($_vq, "vring_virtqueue")->vring->used->idx)- (@cast($_vq, "vring_virtqueue")->last_used_idx) ---> we use this one to verify if the queue is full, which means guest is not able to take buffer from the queue timely if (x<0 && (x+65535)<4096) x = x+65535 if((x==1024) && @cast($_vq, "vring_virtqueue")->vq->callback == callback_addr) netrxcount[x] <<< gettimeofday_s() } probe module("virtio_ring").function("virtqueue_add_inbuf") { y = (@cast($vq, "vring_virtqueue")->vring->avail->idx)- (@cast($vq, "vring_virtqueue")->vring->used->idx) ---> we use this one to verify if we run out of free buffer in avail ring if (y<0 && (y+65535)<4096) y = y+65535 if(@2=="debugon") { if(y==0 && @cast($vq, "vring_virtqueue")->vq->callback == callback_addr) { netrxfreecount[y] <<< gettimeofday_s() printf("no avail ring left seen, printing most recent 5 num free, vq: %lx, current index: %d\n", $vq, recentfreecount) for(i=recentfreecount; i!=((recentfreecount+4) % 5); i=((i+1) % 5)) { printf("index: %d, num free: %d\n", i, recentfree[$vq, i]) } printf("index: %d, num free: %d\n", i, recentfree[$vq, i]) //exit() } } } probe module("virtio_net").statement("virtnet_receive@drivers/net/virtio_net.c:732") { recentfreecount++ recentfreecount = recentfreecount % 5 recentfree[$rq->vq, recentfreecount] = $rq->vq->num_free ---> record the num_free for the last 5 calls to virtnet_receive, so we can see if lowering the bar helps. } Here is the result: no avail ring left seen, printing most recent 5 num free, vq: ffff9c13c1200000, current index: 1 index: 1, num free: 561 index: 2, num free: 305 index: 3, num free: 369 index: 4, num free: 433 index: 0, num free: 497 no avail ring left seen, printing most recent 5 num free, vq: ffff9c13c1200000, current index: 1 index: 1, num free: 543 index: 2, num free: 463 index: 3, num free: 469 index: 4, num free: 476 index: 0, num free: 479 no avail ring left seen, printing most recent 5 num free, vq: ffff9c13c1200000, current index: 2 index: 2, num free: 555 index: 3, num free: 414 index: 4, num free: 420 index: 0, num free: 427 index: 1, num free: 491 We can see in the last 4 calls to virtnet_receive before we run out of free buffer and start to relaim, num_free is quite high. So if we can do the reclaim earlier, it will certainly help. JiangRight, but I think there's no need to put those thing in the commit log. ThanksSure, here is the info: Test setup: iperf3 to generate packets to guest (total 30mins, pps 400k)
Please also note that type of packets e.g TCP or UDP. Thanks
avg packets drop before: 2842 avg packets drop after: 360(-87.3%) Just let me know if it looks good enough. Thx. Jiang
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