From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 43E26C43387 for ; Thu, 27 Dec 2018 10:00:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E92DF214C6 for ; Thu, 27 Dec 2018 10:00:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730699AbeL0KAw (ORCPT ); Thu, 27 Dec 2018 05:00:52 -0500 Received: from mx1.redhat.com ([209.132.183.28]:37536 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727926AbeL0KAw (ORCPT ); Thu, 27 Dec 2018 05:00:52 -0500 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 7615BB0824; Thu, 27 Dec 2018 10:00:51 +0000 (UTC) Received: from [10.72.12.191] (ovpn-12-191.pek2.redhat.com [10.72.12.191]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 1E81A60C66; Thu, 27 Dec 2018 10:00:38 +0000 (UTC) Subject: Re: [PATCH RFC 1/2] virtio-net: bql support To: "Michael S. Tsirkin" Cc: linux-kernel@vger.kernel.org, maxime.coquelin@redhat.com, tiwei.bie@intel.com, wexu@redhat.com, jfreimann@redhat.com, "David S. Miller" , virtualization@lists.linux-foundation.org, netdev@vger.kernel.org References: <20181205225323.12555-1-mst@redhat.com> <20181205225323.12555-2-mst@redhat.com> <21384cb5-99a6-7431-1039-b356521e1bc3@redhat.com> <20181226101528-mutt-send-email-mst@kernel.org> From: Jason Wang Message-ID: <0fa99d9b-e510-d7eb-db1b-831bd7610ce9@redhat.com> Date: Thu, 27 Dec 2018 18:00:36 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20181226101528-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Thu, 27 Dec 2018 10:00:51 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018/12/26 下午11:19, Michael S. Tsirkin wrote: > On Thu, Dec 06, 2018 at 04:17:36PM +0800, Jason Wang wrote: >> On 2018/12/6 上午6:54, Michael S. Tsirkin wrote: >>> When use_napi is set, let's enable BQLs. Note: some of the issues are >>> similar to wifi. It's worth considering whether something similar to >>> commit 36148c2bbfbe ("mac80211: Adjust TSQ pacing shift") might be >>> benefitial. >> >> I've played a similar patch several days before. The tricky part is the mode >> switching between napi and no napi. We should make sure when the packet is >> sent and trakced by BQL,  it should be consumed by BQL as well. I did it by >> tracking it through skb->cb.  And deal with the freeze by reset the BQL >> status. Patch attached. >> >> But when testing with vhost-net, I don't very a stable performance, > So how about increasing TSQ pacing shift then? I can test this. But changing default TCP value is much more than a virtio-net specific thing. > >> it was >> probably because we batch the used ring updating so tx interrupt may come >> randomly. We probably need to implement time bounded coalescing mechanism >> which could be configured from userspace. > I don't think it's reasonable to expect userspace to be that smart ... > Why do we need time bounded? used ring is always updated when ring > becomes empty. We don't add used when means BQL may not see the consumed packet in time. And the delay varies based on the workload since we count packets not bytes or time before doing the batched updating. Thanks > >> Btw, maybe it's time just enable napi TX by default. I get ~10% TCP_RR >> regression on machine without APICv, (haven't found time to test APICv >> machine). But consider it was for correctness, I think it's acceptable? Then >> we can do optimization on top? >> >> >> Thanks >> >> >>> Signed-off-by: Michael S. Tsirkin >>> --- >>> drivers/net/virtio_net.c | 27 +++++++++++++++++++-------- >>> 1 file changed, 19 insertions(+), 8 deletions(-) >>> >>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c >>> index cecfd77c9f3c..b657bde6b94b 100644 >>> --- a/drivers/net/virtio_net.c >>> +++ b/drivers/net/virtio_net.c >>> @@ -1325,7 +1325,8 @@ static int virtnet_receive(struct receive_queue *rq, int budget, >>> return stats.packets; >>> } >>> -static void free_old_xmit_skbs(struct send_queue *sq) >>> +static void free_old_xmit_skbs(struct send_queue *sq, struct netdev_queue *txq, >>> + bool use_napi) >>> { >>> struct sk_buff *skb; >>> unsigned int len; >>> @@ -1347,6 +1348,9 @@ static void free_old_xmit_skbs(struct send_queue *sq) >>> if (!packets) >>> return; >>> + if (use_napi) >>> + netdev_tx_completed_queue(txq, packets, bytes); >>> + >>> u64_stats_update_begin(&sq->stats.syncp); >>> sq->stats.bytes += bytes; >>> sq->stats.packets += packets; >>> @@ -1364,7 +1368,7 @@ static void virtnet_poll_cleantx(struct receive_queue *rq) >>> return; >>> if (__netif_tx_trylock(txq)) { >>> - free_old_xmit_skbs(sq); >>> + free_old_xmit_skbs(sq, txq, true); >>> __netif_tx_unlock(txq); >>> } >>> @@ -1440,7 +1444,7 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget) >>> struct netdev_queue *txq = netdev_get_tx_queue(vi->dev, vq2txq(sq->vq)); >>> __netif_tx_lock(txq, raw_smp_processor_id()); >>> - free_old_xmit_skbs(sq); >>> + free_old_xmit_skbs(sq, txq, true); >>> __netif_tx_unlock(txq); >>> virtqueue_napi_complete(napi, sq->vq, 0); >>> @@ -1505,13 +1509,15 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) >>> struct send_queue *sq = &vi->sq[qnum]; >>> int err; >>> struct netdev_queue *txq = netdev_get_tx_queue(dev, qnum); >>> - bool kick = !skb->xmit_more; >>> + bool more = skb->xmit_more; >>> bool use_napi = sq->napi.weight; >>> + unsigned int bytes = skb->len; >>> + bool kick; >>> /* Free up any pending old buffers before queueing new ones. */ >>> - free_old_xmit_skbs(sq); >>> + free_old_xmit_skbs(sq, txq, use_napi); >>> - if (use_napi && kick) >>> + if (use_napi && !more) >>> virtqueue_enable_cb_delayed(sq->vq); >>> /* timestamp packet in software */ >>> @@ -1552,7 +1558,7 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) >>> if (!use_napi && >>> unlikely(!virtqueue_enable_cb_delayed(sq->vq))) { >>> /* More just got used, free them then recheck. */ >>> - free_old_xmit_skbs(sq); >>> + free_old_xmit_skbs(sq, txq, false); >>> if (sq->vq->num_free >= 2+MAX_SKB_FRAGS) { >>> netif_start_subqueue(dev, qnum); >>> virtqueue_disable_cb(sq->vq); >>> @@ -1560,7 +1566,12 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) >>> } >>> } >>> - if (kick || netif_xmit_stopped(txq)) { >>> + if (use_napi) >>> + kick = __netdev_tx_sent_queue(txq, bytes, more); >>> + else >>> + kick = !more || netif_xmit_stopped(txq); >>> + >>> + if (kick) { >>> if (virtqueue_kick_prepare(sq->vq) && virtqueue_notify(sq->vq)) { >>> u64_stats_update_begin(&sq->stats.syncp); >>> sq->stats.kicks++;