[PATCH RFC v2 4/4] virtio-net: support future packet transmit time
From: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Date: 2021-02-08 18:59:56
Also in:
netdev
Subsystem:
networking drivers, the rest, virtio core, virtio net driver · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds, "Michael S. Tsirkin", Jason Wang
From: Willem de Bruijn <willemb@google.com> Add optional transmit time (SO_TXTIME) offload for virtio-net. The Linux TCP/IP stack tries to avoid bursty transmission and network congestion through pacing: computing an skb delivery time based on congestion information. Userspace protocol implementations can achieve the same with SO_TXTIME. This may also reduce scheduling jitter and improve RTT estimation. Pacing can be implemented in ETF or FQ qdiscs or offloaded to NIC hardware. Allow virtio-net driver to offload for the same reasons. The timestamp straddles (virtual) hardware domains. Like PTP, use international atomic time (CLOCK_TAI) as global clock base. The driver must sync with the device, e.g., through kvm-clock. Changes RFC - RFCv2 - rename from transmit timestamp to future packet transmit time - convert cpu_to_virtioXX to cpu_to_leXX Signed-off-by: Willem de Bruijn <willemb@google.com> --- drivers/net/virtio_net.c | 13 ++++++++++++- include/uapi/linux/virtio_net.h | 1 + 2 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index fc8ecd3a333a..c09d19b97f42 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c@@ -216,6 +216,9 @@ struct virtnet_info { /* Device will pass tx timestamp. Requires has_tx_tstamp */ bool enable_tx_tstamp; + /* Driver will pass CLOCK_TAI delivery time to the device */ + bool has_tx_time; + /* Has control virtqueue */ bool has_cvq;
@@ -1616,6 +1619,8 @@ static int xmit_skb(struct send_queue *sq, struct sk_buff *skb) } if (vi->enable_tx_tstamp && skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP) ht->hdr.flags |= VIRTIO_NET_HDR_F_TSTAMP; + if (vi->has_tx_time && skb->tstamp) + ht->tstamp = cpu_to_le64(skb->tstamp); sg_init_table(sq->sg, skb_shinfo(skb)->nr_frags + (can_push ? 1 : 2)); if (can_push) {
@@ -3221,6 +3226,11 @@ static int virtnet_probe(struct virtio_device *vdev) vi->hdr_len = sizeof(struct virtio_net_hdr_hash_ts); } + if (virtio_has_feature(vdev, VIRTIO_NET_F_TX_TIME)) { + vi->has_tx_time = true; + vi->hdr_len = sizeof(struct virtio_net_hdr_hash_ts); + } + if (virtio_has_feature(vdev, VIRTIO_F_ANY_LAYOUT) || virtio_has_feature(vdev, VIRTIO_F_VERSION_1)) vi->any_header_sg = true;
@@ -3412,7 +3422,8 @@ 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_TX_HASH, VIRTIO_NET_F_RX_TSTAMP, VIRTIO_NET_F_TX_TSTAMP + VIRTIO_NET_F_TX_HASH, VIRTIO_NET_F_RX_TSTAMP, VIRTIO_NET_F_TX_TSTAMP, \ + VIRTIO_NET_F_TX_TIME static unsigned int features[] = { VIRTNET_FEATURES,
diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
index b5d6f0c6cead..7ca99a2ee1a3 100644
--- a/include/uapi/linux/virtio_net.h
+++ b/include/uapi/linux/virtio_net.h@@ -57,6 +57,7 @@ * Steering */ #define VIRTIO_NET_F_CTRL_MAC_ADDR 23 /* Set MAC address */ +#define VIRTIO_NET_F_TX_TIME 53 /* Driver sets TAI delivery time */ #define VIRTIO_NET_F_TX_TSTAMP 54 /* Device sends TAI transmit time */ #define VIRTIO_NET_F_RX_TSTAMP 55 /* Device sends TAI receive time */ #define VIRTIO_NET_F_TX_HASH 56 /* Driver sends hash report */
--
2.30.0.478.g8a0d178c01-goog
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