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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 03B48CCA481 for ; Fri, 15 Jul 2022 08:31:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232487AbiGOIbv (ORCPT ); Fri, 15 Jul 2022 04:31:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55616 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232322AbiGOIbu (ORCPT ); Fri, 15 Jul 2022 04:31:50 -0400 Received: from out30-132.freemail.mail.aliyun.com (out30-132.freemail.mail.aliyun.com [115.124.30.132]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 91157804B5; Fri, 15 Jul 2022 01:31:47 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R971e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045170;MF=xuanzhuo@linux.alibaba.com;NM=1;PH=DS;RN=36;SR=0;TI=SMTPD_---0VJOUor5_1657873898; Received: from localhost(mailfrom:xuanzhuo@linux.alibaba.com fp:SMTPD_---0VJOUor5_1657873898) by smtp.aliyun-inc.com; Fri, 15 Jul 2022 16:31:40 +0800 Message-ID: <1657873703.9301925-1-xuanzhuo@linux.alibaba.com> Subject: Re: [PATCH v11 39/40] virtio_net: support tx queue resize Date: Fri, 15 Jul 2022 16:28:23 +0800 From: Xuan Zhuo To: Jason Wang Cc: Richard Weinberger , Anton Ivanov , Johannes Berg , "Michael S. Tsirkin" , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Hans de Goede , Mark Gross , Vadim Pasternak , Bjorn Andersson , Mathieu Poirier , Cornelia Huck , Halil Pasic , Eric Farman , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , Vincent Whitchurch , linux-um@lists.infradead.org, netdev , platform-driver-x86@vger.kernel.org, linux-remoteproc@vger.kernel.org, linux-s390@vger.kernel.org, kvm , "open list:XDP (eXpress Data Path)" , kangjie.xu@linux.alibaba.com, virtualization References: <20220629065656.54420-1-xuanzhuo@linux.alibaba.com> <20220629065656.54420-40-xuanzhuo@linux.alibaba.com> <102d3b83-1ae9-a59a-16ce-251c22b7afb0@redhat.com> <1656986432.1164997-2-xuanzhuo@linux.alibaba.com> In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: platform-driver-x86@vger.kernel.org On Fri, 8 Jul 2022 14:23:57 +0800, Jason Wang wrote: > On Tue, Jul 5, 2022 at 10:01 AM Xuan Zhuo wr= ote: > > > > On Mon, 4 Jul 2022 11:45:52 +0800, Jason Wang wro= te: > > > > > > =E5=9C=A8 2022/6/29 14:56, Xuan Zhuo =E5=86=99=E9=81=93: > > > > This patch implements the resize function of the tx queues. > > > > Based on this function, it is possible to modify the ring num of the > > > > queue. > > > > > > > > Signed-off-by: Xuan Zhuo > > > > --- > > > > drivers/net/virtio_net.c | 48 +++++++++++++++++++++++++++++++++++= +++++ > > > > 1 file changed, 48 insertions(+) > > > > > > > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > > > > index 6ab16fd193e5..fd358462f802 100644 > > > > --- a/drivers/net/virtio_net.c > > > > +++ b/drivers/net/virtio_net.c > > > > @@ -135,6 +135,9 @@ struct send_queue { > > > > struct virtnet_sq_stats stats; > > > > > > > > struct napi_struct napi; > > > > + > > > > + /* Record whether sq is in reset state. */ > > > > + bool reset; > > > > }; > > > > > > > > /* Internal representation of a receive virtqueue */ > > > > @@ -279,6 +282,7 @@ struct padded_vnet_hdr { > > > > }; > > > > > > > > static void virtnet_rq_free_unused_buf(struct virtqueue *vq, void= *buf); > > > > +static void virtnet_sq_free_unused_buf(struct virtqueue *vq, void = *buf); > > > > > > > > static bool is_xdp_frame(void *ptr) > > > > { > > > > @@ -1603,6 +1607,11 @@ static void virtnet_poll_cleantx(struct rece= ive_queue *rq) > > > > return; > > > > > > > > if (__netif_tx_trylock(txq)) { > > > > + if (READ_ONCE(sq->reset)) { > > > > + __netif_tx_unlock(txq); > > > > + return; > > > > + } > > > > + > > > > do { > > > > virtqueue_disable_cb(sq->vq); > > > > free_old_xmit_skbs(sq, true); > > > > @@ -1868,6 +1877,45 @@ static int virtnet_rx_resize(struct virtnet_= info *vi, > > > > return err; > > > > } > > > > > > > > +static int virtnet_tx_resize(struct virtnet_info *vi, > > > > + struct send_queue *sq, u32 ring_num) > > > > +{ > > > > + struct netdev_queue *txq; > > > > + int err, qindex; > > > > + > > > > + qindex =3D sq - vi->sq; > > > > + > > > > + virtnet_napi_tx_disable(&sq->napi); > > > > + > > > > + txq =3D netdev_get_tx_queue(vi->dev, qindex); > > > > + > > > > + /* 1. wait all ximt complete > > > > + * 2. fix the race of netif_stop_subqueue() vs netif_start_subq= ueue() > > > > + */ > > > > + __netif_tx_lock_bh(txq); > > > > + > > > > + /* Prevent rx poll from accessing sq. */ > > > > + WRITE_ONCE(sq->reset, true); > > > > > > > > > Can we simply disable RX NAPI here? > > > > Disable rx napi is indeed a simple solution. But I hope that when deali= ng with > > tx, it will not affect rx. > > Ok, but I think we've already synchronized with tx lock here, isn't it? Yes, do you have any questions about WRITE_ONCE()? There is a set false ope= ration later, I did not use lock there, so I used WRITE/READ_ONCE uniformly. Thanks. > > Thanks > > > > > Thanks. > > > > > > > > > > Thanks > > > > > > > > > > + > > > > + /* Prevent the upper layer from trying to send packets. */ > > > > + netif_stop_subqueue(vi->dev, qindex); > > > > + > > > > + __netif_tx_unlock_bh(txq); > > > > + > > > > + err =3D virtqueue_resize(sq->vq, ring_num, virtnet_sq_free_unus= ed_buf); > > > > + if (err) > > > > + netdev_err(vi->dev, "resize tx fail: tx queue index: %d= err: %d\n", qindex, err); > > > > + > > > > + /* Memory barrier before set reset and start subqueue. */ > > > > + smp_mb(); > > > > + > > > > + WRITE_ONCE(sq->reset, false); > > > > + netif_tx_wake_queue(txq); > > > > + > > > > + virtnet_napi_tx_enable(vi, sq->vq, &sq->napi); > > > > + return err; > > > > +} > > > > + > > > > /* > > > > * Send command via the control virtqueue and check status. Comm= ands > > > > * supported by the hypervisor, as indicated by feature bits, sho= uld > > > > > >