| Message ID | 20221221120618.652074-1-alvaro.karsz@solid-run.com (mailing list archive) |
|---|---|
| State | Rejected |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | virtio_net: send notification coalescing command only if value changed | expand |
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@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
> 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
On Wed, Dec 21, 2022 at 02:44:21PM +0200, Alvaro Karsz wrote: > > 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 We'll always just do 2 commands, right? I don't think we should bother at this point. It might not be completely redundant. E.g. if a card lost the config resending it might help fix things.
> We'll always just do 2 commands, right? This is my point, we are sending 2 commands at the moment, even though one of them may be unnecessary. > E.g. if a card lost the config resending it might help fix things. How can it lose the config? We can say the same about every command sent through the control vq. > I don't think we should bother at this point. Ok, I'll drop it. Alvaro
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; }
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@solid-run.com> --- drivers/net/virtio_net.c | 48 ++++++++++++++++++++++------------------ 1 file changed, 27 insertions(+), 21 deletions(-)