Michael S. Tsirkin
2022-Dec-21 12:33 UTC
[PATCH] virtio_net: send notification coalescing command only if value changed
On Wed, Dec 21, 2022 at 02:06:18PM +0200, Alvaro Karsz wrote:> Don't send a VIRTIO_NET_CTRL_NOTF_COAL_TX_SET or > VIRTIO_NET_CTRL_NOTF_COAL_RX_SET command if the coalescing parameters > haven't changed. > > Signed-off-by: Alvaro Karsz <alvaro.karsz at solid-run.com>Why do we bother? Resending needs more code and helps reliability ...> --- > drivers/net/virtio_net.c | 48 ++++++++++++++++++++++------------------ > 1 file changed, 27 insertions(+), 21 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 7723b2a49d8..1d7118de62a 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -2760,31 +2760,37 @@ static int virtnet_send_notf_coal_cmds(struct virtnet_info *vi, > struct virtio_net_ctrl_coal_tx coal_tx; > struct virtio_net_ctrl_coal_rx coal_rx; > > - 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; > + if (ec->tx_coalesce_usecs != vi->tx_usecs || > + ec->tx_max_coalesced_frames != vi->tx_max_packets) { > + 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; > + /* 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 (ec->rx_coalesce_usecs != vi->rx_usecs || > + ec->rx_max_coalesced_frames != vi->rx_max_packets) { > + 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; > + 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; > + /* Save parameters */ > + vi->rx_usecs = ec->rx_coalesce_usecs; > + vi->rx_max_packets = ec->rx_max_coalesced_frames; > + } > > return 0; > } > -- > 2.32.0
Alvaro Karsz
2022-Dec-21 12:44 UTC
[PATCH] virtio_net: send notification coalescing command only if value changed
> Why do we bother? Resending needs more code and helps > reliability ...It just seems unnecessary. If a user changes just one parameter: $ ethtool -C <iface> tx-usecs 30 It will trigger 2 commands, including VIRTIO_NET_CTRL_NOTF_COAL_RX_SET, even though no rx parameter changed. If we'll add more ethtool coalescing parameters, changing one of the new parameter will trigger meaningless VIRTIO_NET_CTRL_NOTF_COAL_RX_SET and VIRTIO_NET_CTRL_NOTF_COAL_TX_SET commands. Alvaro