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Message-Id: <20230811065512.22190-2-hengqi@linux.alibaba.com> Date: Fri, 11 Aug 2023 14:55:05 +0800 From: Heng Qi <hengqi@...ux.alibaba.com> To: "Michael S . Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>, netdev@...r.kernel.org, virtualization@...ts.linux-foundation.org Cc: "David S . Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Jesper Dangaard Brouer <hawk@...nel.org>, John Fastabend <john.fastabend@...il.com>, Xuan Zhuo <xuanzhuo@...ux.alibaba.com> Subject: [PATCH net-next 1/8] virtio-net: initially change the value of tx-frames Background: 1. Commit 0c465be183c7 ("virtio_net: ethtool tx napi configuration") uses tx-frames to toggle napi_tx (0 off and 1 on) if notification coalescing is not supported. 2. Commit 31c03aef9bc2 ("virtio_net: enable napi_tx by default") enables napi_tx for all txqs by default. Status: When virtio-net supports notification coalescing, after initialization, tx-frames is 0 and napi_tx is true. Problem: 1. When the user only wants to set rx coalescing params using ethtool -C eth0 rx-usecs 10, or ethtool -Q eth0 queue_mask 0x1 -C rx-usecs 10, these cmds will carry tx-frames as 0, causing the napi_tx switching condition is satisfied. Then the user gets: netlink error: Device or resource busy. The same happens when trying to set rx-frames, adaptive_{rx, tx}. 2. When notification coalescing is not supported, switching napi_tx is a way to achieve coalescing. But now coalescing is supported, we don't need tx-frames to toggle napi_tx anymore. 3. The value of supported tx-frames cannot be set arbitrarily. When setting 0 and non-zero value, if the device is up, the user will always get EBUSY warning. Not intuitive. Result: When notification coalescing feature is negotiated, initially change the value of tx-frames to be consistent with napi_tx. Reported-by: Xiaoming Zhao <zxm377917@...baba-inc.com> Signed-off-by: Heng Qi <hengqi@...ux.alibaba.com> --- drivers/net/virtio_net.c | 42 +++++++++++++++++++++++++++++++++------- 1 file changed, 35 insertions(+), 7 deletions(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 82f9b899b938..3b254f778e7e 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -4376,13 +4376,6 @@ static int virtnet_probe(struct virtio_device *vdev) dev->xdp_features |= NETDEV_XDP_ACT_RX_SG; } - if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_NOTF_COAL)) { - vi->intr_coal_rx.max_usecs = 0; - vi->intr_coal_tx.max_usecs = 0; - vi->intr_coal_tx.max_packets = 0; - vi->intr_coal_rx.max_packets = 0; - } - if (virtio_has_feature(vdev, VIRTIO_NET_F_HASH_REPORT)) vi->has_rss_hash_report = true; @@ -4457,6 +4450,41 @@ static int virtnet_probe(struct virtio_device *vdev) if (err) goto free; + if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_NOTF_COAL)) { + vi->intr_coal_rx.max_usecs = 0; + vi->intr_coal_tx.max_usecs = 0; + vi->intr_coal_rx.max_packets = 0; + + /* Why is this needed? + * If without this setting, consider that when VIRTIO_NET_F_NOTF_COAL is + * negotiated and napi_tx is initially true: when the user sets non tx-frames + * parameters, such as the following cmd or others, + * ethtool -C eth0 rx-usecs 10. + * Then + * 1. ethtool_set_coalesce() first calls virtnet_get_coalesce() to get + * the last parameters except rx-usecs. If tx-frames has never been set before, + * virtnet_get_coalesce() returns with tx-frames=0 in the parameters. + * 2. virtnet_set_coalesce() is then called, according to 1: + * ec->tx_max_coalesced_frames=0. Now napi_tx switching condition is met. + * 3. If the device is up, the user setting fails: + * "netlink error: Device or resource busy" + * This is not intuitive. Therefore, we keep napi_tx state consistent with + * tx-frames when VIRTIO_NET_F_NOTF_COAL is negotiated. This behavior is + * compatible with before. + */ + if (vi->sq[0].napi.weight) + vi->intr_coal_tx.max_packets = 1; + else + vi->intr_coal_tx.max_packets = 0; + } + + if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_VQ_NOTF_COAL)) { + /* The reason is the same as VIRTIO_NET_F_NOTF_COAL. */ + for (i = 0; i < vi->max_queue_pairs; i++) + if (vi->sq[i].napi.weight) + vi->sq[i].intr_coal.max_packets = 1; + } + #ifdef CONFIG_SYSFS if (vi->mergeable_rx_bufs) dev->sysfs_rx_queue_group = &virtio_net_mrg_rx_group; -- 2.19.1.6.gb485710b
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