Messages in this thread | | | Subject | Re: [PATCH] virtio-net: lower min ring num_free for efficiency | From | Jason Wang <> | Date | Thu, 15 Aug 2019 11:17:18 +0800 |
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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. >> >> Thanks >> >> >>> Signed-off-by: jiangkidd <jiangkidd@hotmail.com> >>> --- >>> 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 400k
Why 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%)
Thanks
> > > Data 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. > > Jiang
Right, but I think there's no need to put those thing in the commit log.
Thanks
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