The feature supports two coalescing modes: - Time-based: delay notifications up to N microseconds - Count-based: delay until N packets are processed
Implementation details: - Added VIRTIO_NET_CTRL_NOTF_COAL class handling in control virtqueue - RX path: batches notifications based on packet count or timeout - TX path: leverages the unified dispatcher to dynamically enable timer-based coalescing when guest configures it via ethtool - Coalescing parameters persist across live migration Note: When tx=timer is configured at VM launch, the coalescing feature is automatically disabled because tx=timer already introduces a fixed 150µs delay for packet batching, making notification coalescing redundant. Signed-off-by: Koushik Dutta <[email protected]> --- hw/core/machine.c | 1 + hw/net/virtio-net.c | 176 +++++++++++++++++++++++++++++++-- include/hw/virtio/virtio-net.h | 7 ++ net/passt.c | 1 + net/tap.c | 1 + net/vhost-user.c | 1 + net/vhost-vdpa.c | 1 + 7 files changed, 182 insertions(+), 6 deletions(-) diff --git a/hw/core/machine.c b/hw/core/machine.c index 4d8b15d99e..55ee886f41 100644 --- a/hw/core/machine.c +++ b/hw/core/machine.c @@ -43,6 +43,7 @@ GlobalProperty hw_compat_11_0[] = { { "chardev-vc", "encoding", "cp437" }, { "tpm-crb", "cap-chunk", "off" }, { "tpm-crb", "x-allow-chunk-migration", "off" }, + { TYPE_VIRTIO_NET, "vq_notf_coal", "off" }, }; const size_t hw_compat_11_0_len = G_N_ELEMENTS(hw_compat_11_0); diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c index 319842cf28..4de6aa3b23 100644 --- a/hw/net/virtio-net.c +++ b/hw/net/virtio-net.c @@ -157,6 +157,16 @@ static void flush_or_purge_queued_packets(NetClientState *nc) * - we could suppress RX interrupt if we were so inclined. */ +static void virtio_net_rx_notify(void *opaque) +{ + VirtIONetQueue *q = opaque; + VirtIONet *n = q->n; + VirtIODevice *vdev = VIRTIO_DEVICE(n); + + q->rx_pkt_cnt = 0; + virtio_notify(vdev, q->rx_vq); +} + static void virtio_net_get_config(VirtIODevice *vdev, uint8_t *config) { VirtIONet *n = VIRTIO_NET(vdev); @@ -1004,6 +1014,56 @@ static void virtio_net_set_features(VirtIODevice *vdev, static void virtio_net_tx_timer(void *opaque); +static int virtio_net_handle_coal(VirtIONet *n, uint8_t cmd, + struct iovec *iov, unsigned int iov_cnt) +{ + struct virtio_net_ctrl_coal coal; + VirtIONetQueue *q; + size_t s; + int i; + + s = iov_to_buf(iov, iov_cnt, 0, &coal, sizeof(coal)); + if (s != sizeof(coal)) { + return VIRTIO_NET_ERR; + } + + if (cmd == VIRTIO_NET_CTRL_NOTF_COAL_RX_SET) { + for (i = 0; i < n->max_queue_pairs; i++) { + q = &n->vqs[i]; + q->rx_coal_usecs = le32_to_cpu(coal.max_usecs); + q->rx_coal_packets = le32_to_cpu(coal.max_packets); + if (q->rx_coal_usecs > 0) { + if (!q->rx_timer) { + q->rx_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, + virtio_net_rx_notify, + q); + } + } else { + g_clear_pointer(&q->rx_timer, timer_free); + } + } + } else if (cmd == VIRTIO_NET_CTRL_NOTF_COAL_TX_SET) { + for (i = 0; i < n->max_queue_pairs; i++) { + q = &n->vqs[i]; + q->tx_coal_usecs = le32_to_cpu(coal.max_usecs); + q->tx_coal_packets = le32_to_cpu(coal.max_packets); + /* Converted us to ns */ + n->tx_timeout = q->tx_coal_usecs * 1000; + if (q->tx_coal_usecs > 0) { + if (!q->tx_timer) { + q->tx_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, + virtio_net_tx_timer, + q); + } + } else { + g_clear_pointer(&q->tx_timer, timer_free); + } + } + } + + return VIRTIO_NET_OK; +} + static int virtio_net_handle_rx_mode(VirtIONet *n, uint8_t cmd, struct iovec *iov, unsigned int iov_cnt) { @@ -1583,6 +1643,8 @@ size_t virtio_net_handle_ctrl_iov(VirtIODevice *vdev, status = virtio_net_handle_mq(n, ctrl.cmd, iov, out_num); } else if (ctrl.class == VIRTIO_NET_CTRL_GUEST_OFFLOADS) { status = virtio_net_handle_offloads(n, ctrl.cmd, iov, out_num); + } else if (ctrl.class == VIRTIO_NET_CTRL_NOTF_COAL) { + status = virtio_net_handle_coal(n, ctrl.cmd, iov, out_num); } s = iov_from_buf(in_sg, in_num, 0, &status, sizeof(status)); @@ -2042,7 +2104,23 @@ static ssize_t virtio_net_receive_rcu(NetClientState *nc, const uint8_t *buf, } virtqueue_flush(q->rx_vq, i); - virtio_notify(vdev, q->rx_vq); + + /* rx coalescing */ + q->rx_pkt_cnt += i; + if (q->rx_coal_usecs == 0 || q->rx_pkt_cnt >= q->rx_coal_packets) { + if (q->rx_timer) { + timer_del(q->rx_timer); + } + virtio_net_rx_notify(q); + } else { + if (q->rx_timer) { + if (!timer_pending(q->rx_timer)) { + timer_mod(q->rx_timer, + qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + + q->rx_coal_usecs * 1000); + } + } + } return size; @@ -2900,6 +2978,12 @@ static void virtio_net_tx_timer(void *opaque) if (ret == -EBUSY || ret == -EINVAL) { return; } + if (q->tx_pkt_cnt < ret) { + q->tx_pkt_cnt = 0; + } else { + q->tx_pkt_cnt -= ret; + } + /* * If we flush a full burst of packets, assume there are * more coming and immediately rearm @@ -2919,6 +3003,7 @@ static void virtio_net_tx_timer(void *opaque) ret = virtio_net_flush_tx(q); if (ret > 0) { virtio_queue_set_notification(q->tx_vq, 0); + q->tx_pkt_cnt -= ret; q->tx_waiting = 1; timer_mod(q->tx_timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + n->tx_timeout); @@ -2985,6 +3070,15 @@ static void virtio_net_handle_tx_dispatch(VirtIODevice *vdev, VirtQueue *vq) virtio_net_tx_timer, q); } virtio_net_handle_tx_timer(vdev, vq); + } else if (q->tx_coal_usecs > 0 && q->tx_timer) { + q->tx_pkt_cnt++; + if (q->tx_pkt_cnt < q->tx_coal_packets) { + virtio_net_handle_tx_timer(vdev, vq); + } else { + q->tx_pkt_cnt = 0; + timer_del(q->tx_timer); + virtio_net_handle_tx_bh(vdev, vq); + } } else { virtio_net_handle_tx_bh(vdev, vq); } @@ -3006,6 +3100,12 @@ static void virtio_net_add_queue(VirtIONet *n, int index) &DEVICE(vdev)->mem_reentrancy_guard); n->vqs[index].tx_waiting = 0; + n->vqs[index].rx_pkt_cnt = 0; + n->vqs[index].tx_pkt_cnt = 0; + n->vqs[index].rx_coal_usecs = 0; + n->vqs[index].tx_coal_usecs = 0; + n->vqs[index].rx_coal_packets = 0; + n->vqs[index].tx_coal_packets = 0; n->vqs[index].n = n; } @@ -3018,10 +3118,12 @@ static void virtio_net_del_queue(VirtIONet *n, int index) qemu_purge_queued_packets(nc); virtio_del_queue(vdev, index * 2); - if (q->tx_timer) { - timer_free(q->tx_timer); - q->tx_timer = NULL; - } else { + + /* Cleanup coalescing timers */ + g_clear_pointer(&q->rx_timer, timer_free); + g_clear_pointer(&q->tx_timer, timer_free); + + if (q->tx_bh) { qemu_bh_delete(q->tx_bh); q->tx_bh = NULL; } @@ -3098,6 +3200,13 @@ static void virtio_net_get_features(VirtIODevice *vdev, uint64_t *features, virtio_features_or(features, features, n->host_features_ex); virtio_add_feature_ex(features, VIRTIO_NET_F_MAC); + if (n->tx_timer_activate) { + virtio_clear_feature_ex(features, VIRTIO_NET_F_NOTF_COAL); + } else { + if (!virtio_has_feature(*features, VIRTIO_NET_F_NOTF_COAL)) { + *features &= ~(1ULL << VIRTIO_NET_F_NOTF_COAL); + } + } if (!peer_has_vnet_hdr(n)) { virtio_clear_feature_ex(features, VIRTIO_NET_F_CSUM); @@ -3252,6 +3361,27 @@ static int virtio_net_post_load_device(void *opaque, int version_id) } virtio_net_commit_rss_config(n); + + for (i = 0; i < n->max_queue_pairs; i++) { + VirtIONetQueue *q = &n->vqs[i]; + if (q->rx_coal_usecs > 0) { + if (!q->rx_timer) { + q->rx_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, + virtio_net_rx_notify, + q); + } + } + + if (q->tx_coal_usecs > 0) { + n->tx_timeout = q->tx_coal_usecs * 1000; + if (!q->tx_timer) { + q->tx_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, + virtio_net_tx_timer, + q); + } + } + } + return 0; } @@ -3271,13 +3401,41 @@ static int virtio_net_post_load_virtio(VirtIODevice *vdev) return 0; } +static bool virtio_net_queue_notf_coal_needed(void *opaque) +{ + VirtIONetQueue *q = opaque; + VirtIONet *n = q->n; + + return virtio_vdev_has_feature(VIRTIO_DEVICE(n), VIRTIO_NET_F_NOTF_COAL); +} + +static const VMStateDescription vmstate_virtio_net_queue_notf_coal = { + .name = "virtio-net-queue-tx_waiting/notf-coal", + .version_id = 1, + .minimum_version_id = 1, + .needed = virtio_net_queue_notf_coal_needed, + .fields = (const VMStateField[]) { + VMSTATE_UINT32(rx_coal_usecs, VirtIONetQueue), + VMSTATE_UINT32(tx_coal_usecs, VirtIONetQueue), + VMSTATE_UINT32(rx_coal_packets, VirtIONetQueue), + VMSTATE_UINT32(tx_coal_packets, VirtIONetQueue), + VMSTATE_UINT32(rx_pkt_cnt, VirtIONetQueue), + VMSTATE_UINT32(tx_pkt_cnt, VirtIONetQueue), + VMSTATE_END_OF_LIST() + }, +}; + /* tx_waiting field of a VirtIONetQueue */ static const VMStateDescription vmstate_virtio_net_queue_tx_waiting = { .name = "virtio-net-queue-tx_waiting", .fields = (const VMStateField[]) { VMSTATE_UINT32(tx_waiting, VirtIONetQueue), VMSTATE_END_OF_LIST() - }, + }, + .subsections = (const VMStateDescription * const []) { + &vmstate_virtio_net_queue_notf_coal, + NULL + } }; static bool max_queue_pairs_gt_1(void *opaque, int version_id) @@ -3982,6 +4140,10 @@ static void virtio_net_device_realize(DeviceState *dev, Error **errp) if (n->net_conf.tx && strcmp(n->net_conf.tx, "timer") == 0) { n->tx_timer_activate = true; + if (n->host_features & (1ULL << VIRTIO_NET_F_NOTF_COAL)) { + warn_report("virtio-net: 'vq_notf_coal' is incompatible with 'tx=timer'," + "disabling notification coalescing"); + } } n->net_conf.tx_queue_size = MIN(virtio_net_max_tx_queue_size(n), @@ -4272,6 +4434,8 @@ static const Property virtio_net_properties[] = { VIRTIO_NET_F_GUEST_USO6, true), DEFINE_PROP_BIT64("host_uso", VirtIONet, host_features, VIRTIO_NET_F_HOST_USO, true), + DEFINE_PROP_BIT64("vq_notf_coal", VirtIONet, host_features, + VIRTIO_NET_F_NOTF_COAL, false), DEFINE_PROP_ON_OFF_AUTO_BIT64("hash-ipv4", VirtIONet, rss_data.specified_hash_types, VIRTIO_NET_HASH_REPORT_IPv4 - 1, diff --git a/include/hw/virtio/virtio-net.h b/include/hw/virtio/virtio-net.h index a4eb3f407e..550aaea2be 100644 --- a/include/hw/virtio/virtio-net.h +++ b/include/hw/virtio/virtio-net.h @@ -159,12 +159,19 @@ typedef struct VirtIONetQueue { VirtQueue *rx_vq; VirtQueue *tx_vq; QEMUTimer *tx_timer; + QEMUTimer *rx_timer; QEMUBH *tx_bh; uint32_t tx_waiting; struct { VirtQueueElement *elem; } async_tx; struct VirtIONet *n; + uint32_t rx_coal_usecs; /* RX interrupt coalescing timeout (microseconds) */ + uint32_t rx_coal_packets; /* RX packet count threshold for coalescing */ + uint32_t rx_pkt_cnt; /* Current RX packet count since last notification */ + uint32_t tx_coal_usecs; /* TX interrupt coalescing timeout (microseconds) */ + uint32_t tx_coal_packets; /* TX packet count threshold for coalescing */ + uint32_t tx_pkt_cnt; /* Current TX packet count since last notification */ } VirtIONetQueue; struct VirtIONet { diff --git a/net/passt.c b/net/passt.c index 45440c399b..43b36ed8c5 100644 --- a/net/passt.c +++ b/net/passt.c @@ -52,6 +52,7 @@ static const int user_feature_bits[] = { VIRTIO_NET_F_GUEST_USO4, VIRTIO_NET_F_GUEST_USO6, VIRTIO_NET_F_HOST_USO, + VIRTIO_NET_F_NOTF_COAL, /* This bit implies RARP isn't sent by QEMU out of band */ VIRTIO_NET_F_GUEST_ANNOUNCE, diff --git a/net/tap.c b/net/tap.c index 57ffb09885..e6ddbc1eb1 100644 --- a/net/tap.c +++ b/net/tap.c @@ -63,6 +63,7 @@ static const int kernel_feature_bits[] = { VIRTIO_F_NOTIFICATION_DATA, VIRTIO_NET_F_RSC_EXT, VIRTIO_NET_F_HASH_REPORT, + VIRTIO_NET_F_NOTF_COAL, VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO, VIRTIO_NET_F_HOST_UDP_TUNNEL_GSO, VHOST_INVALID_FEATURE_BIT diff --git a/net/vhost-user.c b/net/vhost-user.c index 2d0fc49b4d..f1e9b7a038 100644 --- a/net/vhost-user.c +++ b/net/vhost-user.c @@ -54,6 +54,7 @@ static const int user_feature_bits[] = { VIRTIO_NET_F_GUEST_USO4, VIRTIO_NET_F_GUEST_USO6, VIRTIO_NET_F_HOST_USO, + VIRTIO_NET_F_NOTF_COAL, /* This bit implies RARP isn't sent by QEMU out of band */ VIRTIO_NET_F_GUEST_ANNOUNCE, diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c index f1523697e2..0dcd6fb9f1 100644 --- a/net/vhost-vdpa.c +++ b/net/vhost-vdpa.c @@ -70,6 +70,7 @@ static const int vdpa_feature_bits[] = { VIRTIO_NET_F_CTRL_RX, VIRTIO_NET_F_CTRL_RX_EXTRA, VIRTIO_NET_F_CTRL_VLAN, + VIRTIO_NET_F_NOTF_COAL, VIRTIO_NET_F_CTRL_VQ, VIRTIO_NET_F_GSO, VIRTIO_NET_F_GUEST_CSUM, -- 2.53.0
