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[109.67.15.113]) by smtp.gmail.com with ESMTPSA id q17sm2178361wrr.53.2020.12.16.01.23.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 16 Dec 2020 01:23:19 -0800 (PST) Date: Wed, 16 Dec 2020 04:23:16 -0500 From: "Michael S. Tsirkin" To: wangyunjian Cc: netdev@vger.kernel.org, jasowang@redhat.com, willemdebruijn.kernel@gmail.com, virtualization@lists.linux-foundation.org, jerry.lilijun@huawei.com, chenchanghu@huawei.com, xudingke@huawei.com, brian.huangbin@huawei.com Subject: Re: [PATCH net v2 2/2] vhost_net: fix high cpu load when sendmsg fails Message-ID: <20201216042027-mutt-send-email-mst@kernel.org> References: <6b4c5fff8705dc4b5b6a25a45c50f36349350c73.1608065644.git.wangyunjian@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6b4c5fff8705dc4b5b6a25a45c50f36349350c73.1608065644.git.wangyunjian@huawei.com> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, Dec 16, 2020 at 04:20:37PM +0800, wangyunjian wrote: > From: Yunjian Wang > > Currently we break the loop and wake up the vhost_worker when > sendmsg fails. When the worker wakes up again, we'll meet the > same error. This will cause high CPU load. To fix this issue, > we can skip this description by ignoring the error. When we > exceeds sndbuf, the return value of sendmsg is -EAGAIN. In > the case we don't skip the description and don't drop packet. Question: with this patch, what happens if sendmsg is interrupted by a signal? > > Signed-off-by: Yunjian Wang > --- > drivers/vhost/net.c | 21 +++++++++------------ > 1 file changed, 9 insertions(+), 12 deletions(-) > > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c > index c8784dfafdd7..3d33f3183abe 100644 > --- a/drivers/vhost/net.c > +++ b/drivers/vhost/net.c > @@ -827,16 +827,13 @@ static void handle_tx_copy(struct vhost_net *net, struct socket *sock) > msg.msg_flags &= ~MSG_MORE; > } > > - /* TODO: Check specific error and bomb out unless ENOBUFS? */ > err = sock->ops->sendmsg(sock, &msg, len); > - if (unlikely(err < 0)) { > + if (unlikely(err == -EAGAIN)) { > vhost_discard_vq_desc(vq, 1); > vhost_net_enable_vq(net, vq); > break; > - } > - if (err != len) > - pr_debug("Truncated TX packet: len %d != %zd\n", > - err, len); > + } else if (unlikely(err != len)) > + vq_err(vq, "Fail to sending packets err : %d, len : %zd\n", err, len); > done: > vq->heads[nvq->done_idx].id = cpu_to_vhost32(vq, head); > vq->heads[nvq->done_idx].len = 0; > @@ -922,7 +919,6 @@ static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock) > msg.msg_flags &= ~MSG_MORE; > } > > - /* TODO: Check specific error and bomb out unless ENOBUFS? */ > err = sock->ops->sendmsg(sock, &msg, len); > if (unlikely(err < 0)) { > if (zcopy_used) { > @@ -931,13 +927,14 @@ static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock) > nvq->upend_idx = ((unsigned)nvq->upend_idx - 1) > % UIO_MAXIOV; > } > - vhost_discard_vq_desc(vq, 1); > - vhost_net_enable_vq(net, vq); > - break; > + if (err == -EAGAIN) { > + vhost_discard_vq_desc(vq, 1); > + vhost_net_enable_vq(net, vq); > + break; > + } > } > if (err != len) > - pr_debug("Truncated TX packet: " > - " len %d != %zd\n", err, len); > + vq_err(vq, "Fail to sending packets err : %d, len : %zd\n", err, len); I'd rather make the pr_debug -> vq_err a separate change, with proper commit log describing motivation. > if (!zcopy_used) > vhost_add_used_and_signal(&net->dev, vq, head, 0); > else > -- > 2.23.0