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Message-ID: <87386ey2iy.fsf@rustcorp.com.au> Date: Tue, 10 Feb 2015 12:02:37 +1030 From: Rusty Russell <rusty@...tcorp.com.au> To: Jason Wang <jasowang@...hat.com>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, virtualization@...ts.linux-foundation.org, mst@...hat.com Cc: pagupta@...hat.com, Jason Wang <jasowang@...hat.com> Subject: Re: [PATCH RFC v5 net-next 4/6] virtio-net: add basic interrupt coalescing support Jason Wang <jasowang@...hat.com> writes: > This patch enables the interrupt coalescing setting through ethtool. The problem is that there's nothing network specific about interrupt coalescing. I can see other devices wanting exactly the same thing, which means we'd deprecate this in the next virtio standard. I think the right answer is to extend like we did with vring_used_event(), eg: 1) Add a new feature VIRTIO_F_RING_COALESCE. 2) Add another a 32-bit field after vring_used_event(), eg: #define vring_used_delay(vr) (*(u32 *)((vr)->avail->ring[(vr)->num + 2])) This loses the ability to coalesce by number of frames, but we can still do number of sg entries, as we do now with used_event, and we could change virtqueue_enable_cb_delayed() to take a precise number if we wanted. My feeling is that this should be a v1.0-only feature though (eg. feature bit 33). Cheers, Rusty. > Cc: Rusty Russell <rusty@...tcorp.com.au> > Cc: Michael S. Tsirkin <mst@...hat.com> > Signed-off-by: Jason Wang <jasowang@...hat.com> > --- > drivers/net/virtio_net.c | 67 +++++++++++++++++++++++++++++++++++++++++ > include/uapi/linux/virtio_net.h | 12 ++++++++ > 2 files changed, 79 insertions(+) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index cc5f5de..2b958fb 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -145,6 +145,11 @@ struct virtnet_info { > > /* Budget for polling tx completion */ > u32 tx_work_limit; > + > + __u32 rx_coalesce_usecs; > + __u32 rx_max_coalesced_frames; > + __u32 tx_coalesce_usecs; > + __u32 tx_max_coalesced_frames; > }; > > struct padded_vnet_hdr { > @@ -1404,12 +1409,73 @@ static void virtnet_get_channels(struct net_device *dev, > channels->other_count = 0; > } > > +static int virtnet_set_coalesce(struct net_device *dev, > + struct ethtool_coalesce *ec) > +{ > + struct virtnet_info *vi = netdev_priv(dev); > + struct scatterlist sg; > + struct virtio_net_ctrl_coalesce c; > + > + if (!vi->has_cvq || > + !virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_COALESCE)) > + return -EOPNOTSUPP; > + if (vi->rx_coalesce_usecs != ec->rx_coalesce_usecs || > + vi->rx_max_coalesced_frames != ec->rx_max_coalesced_frames) { > + c.coalesce_usecs = ec->rx_coalesce_usecs; > + c.max_coalesced_frames = ec->rx_max_coalesced_frames; > + sg_init_one(&sg, &c, sizeof(c)); > + if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_COALESCE, > + VIRTIO_NET_CTRL_COALESCE_RX_SET, > + &sg)) { > + dev_warn(&dev->dev, "Fail to set rx coalescing\n"); > + return -EINVAL; > + } > + vi->rx_coalesce_usecs = ec->rx_coalesce_usecs; > + vi->rx_max_coalesced_frames = ec->rx_max_coalesced_frames; > + } > + > + if (vi->tx_coalesce_usecs != ec->tx_coalesce_usecs || > + vi->tx_max_coalesced_frames != ec->tx_max_coalesced_frames) { > + c.coalesce_usecs = ec->tx_coalesce_usecs; > + c.max_coalesced_frames = ec->tx_max_coalesced_frames; > + sg_init_one(&sg, &c, sizeof(c)); > + if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_COALESCE, > + VIRTIO_NET_CTRL_COALESCE_TX_SET, > + &sg)) { > + dev_warn(&dev->dev, "Fail to set tx coalescing\n"); > + return -EINVAL; > + } > + vi->tx_coalesce_usecs = ec->tx_coalesce_usecs; > + vi->tx_max_coalesced_frames = ec->tx_max_coalesced_frames; > + } > + > + vi->tx_work_limit = ec->tx_max_coalesced_frames_irq; > + > + return 0; > +} > + > +static int virtnet_get_coalesce(struct net_device *dev, > + struct ethtool_coalesce *ec) > +{ > + struct virtnet_info *vi = netdev_priv(dev); > + > + ec->rx_coalesce_usecs = vi->rx_coalesce_usecs; > + ec->rx_max_coalesced_frames = vi->rx_max_coalesced_frames; > + ec->tx_coalesce_usecs = vi->tx_coalesce_usecs; > + ec->tx_max_coalesced_frames = vi->tx_max_coalesced_frames; > + ec->tx_max_coalesced_frames_irq = vi->tx_work_limit; > + > + return 0; > +} > + > static const struct ethtool_ops virtnet_ethtool_ops = { > .get_drvinfo = virtnet_get_drvinfo, > .get_link = ethtool_op_get_link, > .get_ringparam = virtnet_get_ringparam, > .set_channels = virtnet_set_channels, > .get_channels = virtnet_get_channels, > + .set_coalesce = virtnet_set_coalesce, > + .get_coalesce = virtnet_get_coalesce, > }; > > #define MIN_MTU 68 > @@ -2048,6 +2114,7 @@ static unsigned int features[] = { > VIRTIO_NET_F_GUEST_ANNOUNCE, VIRTIO_NET_F_MQ, > VIRTIO_NET_F_CTRL_MAC_ADDR, > VIRTIO_F_ANY_LAYOUT, > + VIRTIO_NET_F_CTRL_COALESCE, > }; > > static struct virtio_driver virtio_net_driver = { > diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h > index b5f1677..332009d 100644 > --- a/include/uapi/linux/virtio_net.h > +++ b/include/uapi/linux/virtio_net.h > @@ -34,6 +34,7 @@ > /* The feature bitmap for virtio net */ > #define VIRTIO_NET_F_CSUM 0 /* Host handles pkts w/ partial csum */ > #define VIRTIO_NET_F_GUEST_CSUM 1 /* Guest handles pkts w/ partial csum */ > +#define VIRTIO_NET_F_CTRL_COALESCE 3 /* Set coalescing */ > #define VIRTIO_NET_F_MAC 5 /* Host has given MAC address. */ > #define VIRTIO_NET_F_GSO 6 /* Host handles pkts w/ any GSO type */ > #define VIRTIO_NET_F_GUEST_TSO4 7 /* Guest can handle TSOv4 in. */ > @@ -202,4 +203,15 @@ struct virtio_net_ctrl_mq { > #define VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MIN 1 > #define VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MAX 0x8000 > > +struct virtio_net_ctrl_coalesce { > + __u32 coalesce_usecs; > + __u32 max_coalesced_frames; > +}; > + > +#define VIRTIO_NET_CTRL_COALESCE 6 > + #define VIRTIO_NET_CTRL_COALESCE_TX_SET 0 > + #define VIRTIO_NET_CTRL_COALESCE_TX_GET 1 > + #define VIRTIO_NET_CTRL_COALESCE_RX_SET 2 > + #define VIRTIO_NET_CTRL_COALESCE_RX_GET 3 > + > #endif /* _LINUX_VIRTIO_NET_H */ > -- > 1.8.3.1 -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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