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Date: Thu, 12 May 2022 05:55:31 -0400
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Alvaro Karsz <alvaro.karsz@...id-run.com>
Cc: netdev@...r.kernel.org, rabeeh@...id-run.com,
Jason Wang <jasowang@...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] net: virtio_net: support interrupt coalescing
On Thu, May 12, 2022 at 11:35:23AM +0300, Alvaro Karsz wrote:
> Control a Virtio network device interrupt coalescing parameters
> using the control virtqueue.
>
> New VirtIO network feature: VIRTIO_NET_F_INTR_COAL.
>
> A device that supports this fetature can receive
> VIRTIO_NET_CTRL_INTR_COAL control commands.
>
> * VIRTIO_NET_CTRL_INTR_COAL_USECS_SET:
> change the rx-usecs and tx-usecs parameters.
>
> rx-usecs - Time to delay an RX interrupt after packet arrival in
> microseconds.
>
> tx-usecs - Time to delay a TX interrupt after a sending a packet
> in microseconds.
>
> * VIRTIO_NET_CTRL_INTR_COAL_FRAMES_SET:
> change the rx-max-frames and tx-max-frames parameters.
>
> rx-max-frames: Number of packets to delay an RX interrupt after
> packet arrival.
>
> tx-max-frames: Number of packets to delay a TX interrupt after
> sending a packet.
>
> Signed-off-by: Alvaro Karsz <alvaro.karsz@...id-run.com>
So first, please at least reserve the feature in the virtio spec.
Preferably add the specification as well.
Here's one way to do it:
https://github.com/oasis-tcs/virtio-spec#use-of-github-issues
> ---
> drivers/net/virtio_net.c | 108 ++++++++++++++++++++++++++++----
> include/uapi/linux/virtio_net.h | 34 +++++++++-
> 2 files changed, 128 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index cbba9d2e8f3..4806c35ddd5 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_frames_max;
> + u32 rx_frames_max;
> +
> unsigned long guest_offloads;
> unsigned long guest_offloads_capable;
>
> @@ -2594,19 +2600,75 @@ static int virtnet_set_coalesce(struct net_device *dev,
> {
> struct virtnet_info *vi = netdev_priv(dev);
> int i, napi_weight;
> + struct scatterlist sgs_usecs, sgs_frames;
> + struct virtio_net_ctrl_coal_frames c_frames;
> + struct virtio_net_ctrl_coal_usec c_usecs;
> + bool update_napi,
> + intr_coal = virtio_has_feature(vi->vdev, VIRTIO_NET_F_INTR_COAL);
> +
> + /* rx_coalesce_usecs/tx_coalesce_usecs are supported only
> + * if VIRTIO_NET_F_INTR_COAL feature is set.
> + */
> + if (!intr_coal && (ec->rx_coalesce_usecs || ec->tx_coalesce_usecs))
> + return -EOPNOTSUPP;
> +
> + if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_INTR_COAL)) {
> + /* Send usec command */
> + c_usecs.tx_usecs = ec->tx_coalesce_usecs;
> + c_usecs.rx_usecs = ec->rx_coalesce_usecs;
> + sg_init_one(&sgs_usecs, &c_usecs, sizeof(c_usecs));
> +
> + if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_INTR_COAL,
> + VIRTIO_NET_CTRL_INTR_COAL_USECS_SET,
> + &sgs_usecs))
> + return -EINVAL;
> +
> + /* Save parameters */
> + vi->tx_usecs = ec->tx_coalesce_usecs;
> + vi->rx_usecs = ec->rx_coalesce_usecs;
> +
> + /* Send frames command */
> + c_frames.tx_frames_max = ec->tx_max_coalesced_frames;
> + c_frames.rx_frames_max = ec->rx_max_coalesced_frames;
> + sg_init_one(&sgs_frames, &c_frames, sizeof(c_frames));
> +
> + if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_INTR_COAL,
> + VIRTIO_NET_CTRL_INTR_COAL_FRAMES_SET,
> + &sgs_frames))
> + return -EINVAL;
> +
> + /* Save parameters */
> + vi->tx_frames_max = ec->tx_max_coalesced_frames;
> + vi->rx_frames_max = 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 interrupt coalesing feature is not set, and we can't update NAPI, return an error */
> + if (!intr_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 Interrupt coalescing feature is not set, return an error.
> + * Otherwise exit without changing the NAPI paremeters
> + */
> + if (!intr_coal)
> + return -EBUSY;
> +
> + goto exit;
> + }
> +
> + for (i = 0; i < vi->max_queue_pairs; i++)
> + vi->sq[i].napi.weight = napi_weight;
> + }
> }
>
> +exit:
> return 0;
> }
>
> @@ -2616,14 +2678,25 @@ 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,
> + .cmd = ETHTOOL_GCOALESCE
> };
> +
> struct virtnet_info *vi = netdev_priv(dev);
> + bool intr_coal = virtio_has_feature(vi->vdev, VIRTIO_NET_F_INTR_COAL);
> +
> + /* Add Interrupt coalescing settings */
> + if (intr_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_frames_max;
> + ec_default.rx_max_coalesced_frames = vi->rx_frames_max;
> + } else {
> + ec_default.rx_max_coalesced_frames = 1;
> + }
>
> memcpy(ec, &ec_default, sizeof(ec_default));
>
> - if (vi->sq[0].napi.weight)
> + if (!intr_coal && vi->sq[0].napi.weight)
> ec->tx_max_coalesced_frames = 1;
>
> return 0;
> @@ -2743,7 +2816,7 @@ 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,
> @@ -3423,6 +3496,8 @@ 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_INTR_COAL,
> "VIRTIO_NET_F_CTRL_VQ"))) {
> return false;
> }
> @@ -3558,6 +3633,13 @@ 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_INTR_COAL)) {
> + vi->rx_usecs = 0;
> + vi->tx_usecs = 0;
> + vi->tx_frames_max = 0;
> + vi->rx_frames_max = 0;
> + }
> +
> if (virtio_has_feature(vdev, VIRTIO_NET_F_HASH_REPORT))
> vi->has_rss_hash_report = true;
>
> @@ -3786,7 +3868,7 @@ 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_INTR_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..b65a4295270 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_INTR_COAL 55 /* Guest can handle Interrupt 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 interrupt coalescing.
> + *
> + * Request the device to change the interrupt coalescing parameters.
> + *
> + * Available with the VIRTIO_NET_F_INTR_COAL feature bit.
> + */
> +#define VIRTIO_NET_CTRL_INTR_COAL 6
> +/*
> + * Set the rx-usecs/tx-usecs patameters.
> + * rx-usecs - Number of microseconds to delay an RX interrupt after packet arrival.
> + * tx-usecs - Number of microseconds to delay a TX interrupt after a sending a packet.
> + */
> +struct virtio_net_ctrl_coal_usec {
> + __u32 tx_usecs;
> + __u32 rx_usecs;
> +};
> +
> +#define VIRTIO_NET_CTRL_INTR_COAL_USECS_SET 0
> +
> +/*
> + * Set the rx-max-frames/tx-max-frames patameters.
> + * rx-max-frames - Number of packets to delay an RX interrupt after packet arrival.
> + * tx-max-frames - Number of packets to delay a TX interrupt after sending a packet.
> + */
> +struct virtio_net_ctrl_coal_frames {
> + __u32 tx_frames_max;
> + __u32 rx_frames_max;
> +};
> +
You want all these to be LE. Native endian's unpredictable in lots of
virt settings.
> +#define VIRTIO_NET_CTRL_INTR_COAL_FRAMES_SET 1
> +
> #endif /* _UAPI_LINUX_VIRTIO_NET_H */
> --
> 2.32.0
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