Re: [PATCH RFC v5 net-next 4/6] virtio-net: add basic interrupt coalescing support
From: Jason Wang
Date: Tue Feb 10 2015 - 01:51:49 EST
On Tue, Feb 10, 2015 at 9:32 AM, Rusty Russell <rusty@xxxxxxxxxxxxxxx>
wrote:
Jason Wang <jasowang@xxxxxxxxxx> 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]))
Yes. This looks better and we don't even need device specific
configuration method.
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.
Can we give a device specific meaning for this? For virtio-net, we want
to expose the coalescing settings through ethtool (tx-frames). And it
was usually used with a timer, so probably another field after
vring_used_delay() for this timer interval to trigger the interrupt if
no new used buffers come after this interval.
My feeling is that this should be a v1.0-only feature though
(eg. feature bit 33).
Yes it should.
Cheers,
Rusty.
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
---
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
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