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Tsirkin" To: Xuan Zhuo Subject: Re: [PATCH v14 37/42] virtio_net: set the default max ring size by find_vqs() Message-ID: <20220815031022-mutt-send-email-mst@kernel.org> References: <20220801063902.129329-1-xuanzhuo@linux.alibaba.com> <20220801063902.129329-38-xuanzhuo@linux.alibaba.com> <20220815015405-mutt-send-email-mst@kernel.org> <1660545303.436073-9-xuanzhuo@linux.alibaba.com> MIME-Version: 1.0 In-Reply-To: <1660545303.436073-9-xuanzhuo@linux.alibaba.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Cc: Vadim Pasternak , linux-remoteproc@vger.kernel.org, Alexei Starovoitov , virtualization@lists.linux-foundation.org, Eric Dumazet , Alexander Gordeev , Anton Ivanov , linux-s390@vger.kernel.org, kvm@vger.kernel.org, Daniel Borkmann , Richard Weinberger , Vincent Whitchurch , John Fastabend , Halil Pasic , Jakub Kicinski , platform-driver-x86@vger.kernel.org, Eric Farman , Jesper Dangaard Brouer , Vasily Gorbik , kangjie.xu@linux.alibaba.com, Heiko Carstens , linux-um@lists.infradead.org, Mark Gross , Hans de Goede , Bjorn Andersson , bpf@vger.kernel.org, Paolo Abeni , Mathieu Poirier , netdev@vger.kernel.org, Cornelia Huck , Sven Schnelle , Johannes Berg , "David S. Miller" X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" On Mon, Aug 15, 2022 at 02:35:03PM +0800, Xuan Zhuo wrote: > On Mon, 15 Aug 2022 02:00:16 -0400, "Michael S. Tsirkin" wrote: > > On Mon, Aug 01, 2022 at 02:38:57PM +0800, Xuan Zhuo wrote: > > > Use virtio_find_vqs_ctx_size() to specify the maximum ring size of tx, > > > rx at the same time. > > > > > > | rx/tx ring size > > > ------------------------------------------- > > > speed == UNKNOWN or < 10G| 1024 > > > speed < 40G | 4096 > > > speed >= 40G | 8192 > > > > > > Call virtnet_update_settings() once before calling init_vqs() to update > > > speed. > > > > > > Signed-off-by: Xuan Zhuo > > > Acked-by: Jason Wang > > > > I've been looking at this patchset because of the resent > > reported crashes, and I'm having second thoughts about this. > > > > Do we really want to second-guess the device supplied > > max ring size? If yes why? > > > > Could you please share some performance data that motivated this > > specific set of numbers? > > > The impact of this value on performance is as follows. The larger the value, the > throughput can be increased, but the delay will also increase accordingly. It is > a maximum limit for the ring size under the corresponding speed. The purpose of > this limitation is not to improve performance, but more to reduce memory usage. > > These data come from many other network cards and some network optimization > experience. > > For example, in the case of speed = 20G, the impact of ring size greater > than 4096 on performance has no meaning. At this time, if the device supports > 8192, we limit it to 4096 through this, the real meaning is to reduce the memory > usage. > > > > > > Also why do we intepret UNKNOWN as "very low"? > > I'm thinking that should definitely be "don't change anything". > > > > Generally speaking, for a network card with a high speed, it will return a > correct speed. But I think it is a good idea to do nothing. > > > Finally if all this makes sense then shouldn't we react when > > speed changes? > > This is the feedback of the network card when it is started, and theoretically > it should not change in the future. Yes it should: Both \field{speed} and \field{duplex} can change, thus the driver is expected to re-read these values after receiving a configuration change notification. Moreover, during probe link can quite reasonably be down. If it is, then speed and duplex might not be correct. > > > > Could you try reverting this and showing performance results > > before and after please? Thanks! > > I hope the above reply can help you, if there is anything else you need me to > cooperate with, I am very happy. > > If you think it's ok, I can resubmit a commit with 'UNKNOW' set to unlimited. I > can submit it with the issue of #30. > > Thanks. > > > > > > > --- > > > drivers/net/virtio_net.c | 42 ++++++++++++++++++++++++++++++++++++---- > > > 1 file changed, 38 insertions(+), 4 deletions(-) > > > > > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > > > index 8a5810bcb839..40532ecbe7fc 100644 > > > --- a/drivers/net/virtio_net.c > > > +++ b/drivers/net/virtio_net.c > > > @@ -3208,6 +3208,29 @@ static unsigned int mergeable_min_buf_len(struct virtnet_info *vi, struct virtqu > > > (unsigned int)GOOD_PACKET_LEN); > > > } > > > > > > +static void virtnet_config_sizes(struct virtnet_info *vi, u32 *sizes) > > > +{ > > > + u32 i, rx_size, tx_size; > > > + > > > + if (vi->speed == SPEED_UNKNOWN || vi->speed < SPEED_10000) { > > > + rx_size = 1024; > > > + tx_size = 1024; > > > + > > > + } else if (vi->speed < SPEED_40000) { > > > + rx_size = 1024 * 4; > > > + tx_size = 1024 * 4; > > > + > > > + } else { > > > + rx_size = 1024 * 8; > > > + tx_size = 1024 * 8; > > > + } > > > + > > > + for (i = 0; i < vi->max_queue_pairs; i++) { > > > + sizes[rxq2vq(i)] = rx_size; > > > + sizes[txq2vq(i)] = tx_size; > > > + } > > > +} > > > + > > > static int virtnet_find_vqs(struct virtnet_info *vi) > > > { > > > vq_callback_t **callbacks; > > > @@ -3215,6 +3238,7 @@ static int virtnet_find_vqs(struct virtnet_info *vi) > > > int ret = -ENOMEM; > > > int i, total_vqs; > > > const char **names; > > > + u32 *sizes; > > > bool *ctx; > > > > > > /* We expect 1 RX virtqueue followed by 1 TX virtqueue, followed by > > > @@ -3242,10 +3266,15 @@ static int virtnet_find_vqs(struct virtnet_info *vi) > > > ctx = NULL; > > > } > > > > > > + sizes = kmalloc_array(total_vqs, sizeof(*sizes), GFP_KERNEL); > > > + if (!sizes) > > > + goto err_sizes; > > > + > > > /* Parameters for control virtqueue, if any */ > > > if (vi->has_cvq) { > > > callbacks[total_vqs - 1] = NULL; > > > names[total_vqs - 1] = "control"; > > > + sizes[total_vqs - 1] = 64; > > > } > > > > > > /* Allocate/initialize parameters for send/receive virtqueues */ > > > @@ -3260,8 +3289,10 @@ static int virtnet_find_vqs(struct virtnet_info *vi) > > > ctx[rxq2vq(i)] = true; > > > } > > > > > > - ret = virtio_find_vqs_ctx(vi->vdev, total_vqs, vqs, callbacks, > > > - names, ctx, NULL); > > > + virtnet_config_sizes(vi, sizes); > > > + > > > + ret = virtio_find_vqs_ctx_size(vi->vdev, total_vqs, vqs, callbacks, > > > + names, sizes, ctx, NULL); > > > if (ret) > > > goto err_find; > > > > > > @@ -3281,6 +3312,8 @@ static int virtnet_find_vqs(struct virtnet_info *vi) > > > > > > > > > err_find: > > > + kfree(sizes); > > > +err_sizes: > > > kfree(ctx); > > > err_ctx: > > > kfree(names); > > > @@ -3630,6 +3663,9 @@ static int virtnet_probe(struct virtio_device *vdev) > > > vi->curr_queue_pairs = num_online_cpus(); > > > vi->max_queue_pairs = max_queue_pairs; > > > > > > + virtnet_init_settings(dev); > > > + virtnet_update_settings(vi); > > > + > > > /* Allocate/initialize the rx/tx queues, and invoke find_vqs */ > > > err = init_vqs(vi); > > > if (err) > > > @@ -3642,8 +3678,6 @@ static int virtnet_probe(struct virtio_device *vdev) > > > netif_set_real_num_tx_queues(dev, vi->curr_queue_pairs); > > > netif_set_real_num_rx_queues(dev, vi->curr_queue_pairs); > > > > > > - virtnet_init_settings(dev); > > > - > > > if (virtio_has_feature(vdev, VIRTIO_NET_F_STANDBY)) { > > > vi->failover = net_failover_create(vi->dev); > > > if (IS_ERR(vi->failover)) { > > > -- > > > 2.31.0 > > _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization