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Date: Thu, 14 Jul 2022 14:08:36 +0800
From: Jason Wang <jasowang@...hat.com>
To: Alvaro Karsz <alvaro.karsz@...id-run.com>, netdev@...r.kernel.org
Cc: "Michael S. Tsirkin" <mst@...hat.com>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH v2] net: virtio_net: notifications coalescing support
在 2022/7/12 19:22, Alvaro Karsz 写道:
> New VirtIO network feature: VIRTIO_NET_F_NOTF_COAL.
>
> Control a Virtio network device notifications coalescing parameters
> using the control virtqueue.
>
> A device that supports this fetature can receive
> VIRTIO_NET_CTRL_NOTF_COAL control commands.
>
> - VIRTIO_NET_CTRL_NOTF_COAL_TX_SET:
> Ask the network device to change the following parameters:
> - tx_usecs: Maximum number of usecs to delay a TX notification.
> - tx_max_packets: Maximum number of packets to send before a
> TX notification.
>
> - VIRTIO_NET_CTRL_NOTF_COAL_RX_SET:
> Ask the network device to change the following parameters:
> - rx_usecs: Maximum number of usecs to delay a RX notification.
> - rx_max_packets: Maximum number of packets to receive before a
> RX notification.
>
> VirtIO spec. patch:
> https://lists.oasis-open.org/archives/virtio-comment/202206/msg00100.html
Note that until this is merged, the patch should be tagged as RFC.
And it looks to me we should target this as net-next instead of net.
>
> Signed-off-by: Alvaro Karsz <alvaro.karsz@...id-run.com>
> ---
> v2:
> - Fix type assignments warnings found with sparse.
> - Fix a few typos.
> ---
> drivers/net/virtio_net.c | 110 ++++++++++++++++++++++++++++----
> include/uapi/linux/virtio_net.h | 34 +++++++++-
> 2 files changed, 130 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 356cf8dd416..7837db0306f 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -261,6 +261,12 @@ struct virtnet_info {
> u8 duplex;
> u32 speed;
>
> + /* Interrupt coalescing settings */
> + u32 tx_usecs;
> + u32 rx_usecs;
> + u32 tx_max_packets;
> + u32 rx_max_packets;
> +
> unsigned long guest_offloads;
> unsigned long guest_offloads_capable;
>
> @@ -2594,19 +2600,76 @@ static int virtnet_set_coalesce(struct net_device *dev,
> {
> struct virtnet_info *vi = netdev_priv(dev);
> int i, napi_weight;
> + struct scatterlist sgs_tx, sgs_rx;
> + struct virtio_net_ctrl_coal_tx coal_tx;
> + struct virtio_net_ctrl_coal_rx coal_rx;
> + bool update_napi,
> + notf_coal = virtio_has_feature(vi->vdev, VIRTIO_NET_F_NOTF_COAL);
> +
> + /* rx_coalesce_usecs/tx_coalesce_usecs are supported only
> + * if VIRTIO_NET_F_NOTF_COAL feature is negotiated.
> + */
> + if (!notf_coal && (ec->rx_coalesce_usecs || ec->tx_coalesce_usecs))
> + return -EOPNOTSUPP;
> +
> + if (notf_coal) {
> + coal_tx.tx_usecs = cpu_to_le32(ec->tx_coalesce_usecs);
> + coal_tx.tx_max_packets = cpu_to_le32(ec->tx_max_coalesced_frames);
> + sg_init_one(&sgs_tx, &coal_tx, sizeof(coal_tx));
> +
> + if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_NOTF_COAL,
> + VIRTIO_NET_CTRL_NOTF_COAL_TX_SET,
> + &sgs_tx))
> + return -EINVAL;
> +
> + /* Save parameters */
> + vi->tx_usecs = ec->tx_coalesce_usecs;
> + vi->tx_max_packets = ec->tx_max_coalesced_frames;
> +
> + coal_rx.rx_usecs = cpu_to_le32(ec->rx_coalesce_usecs);
> + coal_rx.rx_max_packets = cpu_to_le32(ec->rx_max_coalesced_frames);
> + sg_init_one(&sgs_rx, &coal_rx, sizeof(coal_rx));
> +
> + if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_NOTF_COAL,
> + VIRTIO_NET_CTRL_NOTF_COAL_RX_SET,
> + &sgs_rx))
> + return -EINVAL;
> +
> + /* Save parameters */
> + vi->rx_usecs = ec->rx_coalesce_usecs;
> + vi->rx_max_packets = ec->rx_max_coalesced_frames;
> + }
> +
> + /* Should we update NAPI? */
> + update_napi = ec->tx_max_coalesced_frames <= 1 &&
> + ec->rx_max_coalesced_frames == 1;
>
> - if (ec->tx_max_coalesced_frames > 1 ||
> - ec->rx_max_coalesced_frames != 1)
> + /* If notifications coalesing feature is not negotiated,
> + * and we can't update NAPI, return an error
> + */
> + if (!notf_coal && !update_napi)
> return -EINVAL;
>
> - napi_weight = ec->tx_max_coalesced_frames ? NAPI_POLL_WEIGHT : 0;
> - if (napi_weight ^ vi->sq[0].napi.weight) {
> - if (dev->flags & IFF_UP)
> - return -EBUSY;
> - for (i = 0; i < vi->max_queue_pairs; i++)
> - vi->sq[i].napi.weight = napi_weight;
> + if (update_napi) {
> + napi_weight = ec->tx_max_coalesced_frames ? NAPI_POLL_WEIGHT : 0;
> + if (napi_weight ^ vi->sq[0].napi.weight) {
> + if (dev->flags & IFF_UP) {
> + /* If notifications coalescing feature is not negotiated,
> + * return an error, otherwise exit without changing
> + * the NAPI parameters.
> + */
> + if (!notf_coal)
> + return -EBUSY;
> +
> + goto exit;
I think we need to return -EBUSY here regardless whether or not
interrupt coalescing is negotiated.
This is because the driver can work in two modes:
1) tx interrupt mode (tx_max_coalesced_frames = 1)
2) no tx interrupt mode (will do skb_orphan) (tx_max_coalesced_frames = 0)
Mode switching is more easier to be done when the interface is down.
When the coalescing is neogiated, we can stick the above logic:
1) tx interrupt mode (tx_max_coalesced_frames >= 1)
2) no tx interrupt mode (will do skb_orphan) (tx_max_coalesced_frames = 0)
So if no mode switching (no switching between zero and non zero value of
tx_max_coalesced_frames), we don't need an update of napi_weight. But if
it requires a switch, it still needs to be done when the interface is
down (technically it's not a must but it should be another topic/patch).
> + }
> +
> + for (i = 0; i < vi->max_queue_pairs; i++)
> + vi->sq[i].napi.weight = napi_weight;
> + }
> }
>
> +exit:
> return 0;
> }
>
> @@ -2616,14 +2679,25 @@ static int virtnet_get_coalesce(struct net_device *dev,
> struct netlink_ext_ack *extack)
> {
> struct ethtool_coalesce ec_default = {
> - .cmd = ETHTOOL_GCOALESCE,
> - .rx_max_coalesced_frames = 1,
Nit: we can stick to this then we can remove the following "else".
Thanks
> + .cmd = ETHTOOL_GCOALESCE
> };
> +
> struct virtnet_info *vi = netdev_priv(dev);
> + bool notf_coal = virtio_has_feature(vi->vdev, VIRTIO_NET_F_NOTF_COAL);
> +
> + /* Add notifications coalescing settings */
> + if (notf_coal) {
> + ec_default.rx_coalesce_usecs = vi->rx_usecs;
> + ec_default.tx_coalesce_usecs = vi->tx_usecs;
> + ec_default.tx_max_coalesced_frames = vi->tx_max_packets;
> + ec_default.rx_max_coalesced_frames = vi->rx_max_packets;
> + } else {
> + ec_default.rx_max_coalesced_frames = 1;
> + }
>
> memcpy(ec, &ec_default, sizeof(ec_default));
>
> - if (vi->sq[0].napi.weight)
> + if (!notf_coal && vi->sq[0].napi.weight)
> ec->tx_max_coalesced_frames = 1;
>
> return 0;
> @@ -2743,7 +2817,8 @@ static int virtnet_set_rxnfc(struct net_device *dev, struct ethtool_rxnfc *info)
> }
>
> static const struct ethtool_ops virtnet_ethtool_ops = {
> - .supported_coalesce_params = ETHTOOL_COALESCE_MAX_FRAMES,
> + .supported_coalesce_params = ETHTOOL_COALESCE_MAX_FRAMES |
> + ETHTOOL_COALESCE_USECS,
> .get_drvinfo = virtnet_get_drvinfo,
> .get_link = ethtool_op_get_link,
> .get_ringparam = virtnet_get_ringparam,
> @@ -3411,6 +3486,8 @@ static bool virtnet_validate_features(struct virtio_device *vdev)
> VIRTNET_FAIL_ON(vdev, VIRTIO_NET_F_RSS,
> "VIRTIO_NET_F_CTRL_VQ") ||
> VIRTNET_FAIL_ON(vdev, VIRTIO_NET_F_HASH_REPORT,
> + "VIRTIO_NET_F_CTRL_VQ") ||
> + VIRTNET_FAIL_ON(vdev, VIRTIO_NET_F_NOTF_COAL,
> "VIRTIO_NET_F_CTRL_VQ"))) {
> return false;
> }
> @@ -3546,6 +3623,13 @@ static int virtnet_probe(struct virtio_device *vdev)
> if (virtio_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF))
> vi->mergeable_rx_bufs = true;
>
> + if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_NOTF_COAL)) {
> + vi->rx_usecs = 0;
> + vi->tx_usecs = 0;
> + vi->tx_max_packets = 0;
> + vi->rx_max_packets = 0;
> + }
> +
> if (virtio_has_feature(vdev, VIRTIO_NET_F_HASH_REPORT))
> vi->has_rss_hash_report = true;
>
> @@ -3780,7 +3864,7 @@ static struct virtio_device_id id_table[] = {
> VIRTIO_NET_F_CTRL_MAC_ADDR, \
> VIRTIO_NET_F_MTU, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS, \
> VIRTIO_NET_F_SPEED_DUPLEX, VIRTIO_NET_F_STANDBY, \
> - VIRTIO_NET_F_RSS, VIRTIO_NET_F_HASH_REPORT
> + VIRTIO_NET_F_RSS, VIRTIO_NET_F_HASH_REPORT, VIRTIO_NET_F_NOTF_COAL
>
> static unsigned int features[] = {
> VIRTNET_FEATURES,
> diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
> index 3f55a4215f1..29ced55514d 100644
> --- a/include/uapi/linux/virtio_net.h
> +++ b/include/uapi/linux/virtio_net.h
> @@ -56,7 +56,7 @@
> #define VIRTIO_NET_F_MQ 22 /* Device supports Receive Flow
> * Steering */
> #define VIRTIO_NET_F_CTRL_MAC_ADDR 23 /* Set MAC address */
> -
> +#define VIRTIO_NET_F_NOTF_COAL 53 /* Guest can handle notifications coalescing */
> #define VIRTIO_NET_F_HASH_REPORT 57 /* Supports hash report */
> #define VIRTIO_NET_F_RSS 60 /* Supports RSS RX steering */
> #define VIRTIO_NET_F_RSC_EXT 61 /* extended coalescing info */
> @@ -355,4 +355,36 @@ struct virtio_net_hash_config {
> #define VIRTIO_NET_CTRL_GUEST_OFFLOADS 5
> #define VIRTIO_NET_CTRL_GUEST_OFFLOADS_SET 0
>
> +/*
> + * Control notifications coalescing.
> + *
> + * Request the device to change the notifications coalescing parameters.
> + *
> + * Available with the VIRTIO_NET_F_NOTF_COAL feature bit.
> + */
> +#define VIRTIO_NET_CTRL_NOTF_COAL 6
> +/*
> + * Set the tx-usecs/tx-max-packets patameters.
> + * tx-usecs - Maximum number of usecs to delay a TX notification.
> + * tx-max-packets - Maximum number of packets to send before a TX notification.
> + */
> +struct virtio_net_ctrl_coal_tx {
> + __le32 tx_max_packets;
> + __le32 tx_usecs;
> +};
> +
> +#define VIRTIO_NET_CTRL_NOTF_COAL_TX_SET 0
> +
> +/*
> + * Set the rx-usecs/rx-max-packets patameters.
> + * rx-usecs - Maximum number of usecs to delay a RX notification.
> + * rx-max-frames - Maximum number of packets to receive before a RX notification.
> + */
> +struct virtio_net_ctrl_coal_rx {
> + __le32 rx_max_packets;
> + __le32 rx_usecs;
> +};
> +
> +#define VIRTIO_NET_CTRL_NOTF_COAL_RX_SET 1
> +
> #endif /* _UAPI_LINUX_VIRTIO_NET_H */
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