Implement VirtIO Network Notification Coalescing (Bit 53). This allows the guest to manage interrupt frequency using ethtool -C for both RX and TX paths.
- Added VIRTIO_NET_F_NOTF_COAL to host features. - Implemented VIRTIO_NET_CTRL_NOTF_COAL class handling in virtio_net_handle_ctrl_iov. - Added logic to store and apply rx/tx usecs and max_packets. - Added packet counters and threshold logic for both RX and TX data paths. - Dynamic Dispatcher: Implemented a dispatcher mechanism that dynamically switches/activates the notification callback logic only after the guest enables TX coalescing via ethtool. This reduces interrupt overhead by batching notifications based on either a packet count or a time-based threshold. Signed-off-by: Koushik Dutta <[email protected]> --- hw/net/virtio-net.c | 114 ++++++++++++++++++++++++----- hw/virtio/vhost-shadow-virtqueue.c | 1 + hw/virtio/vhost-vdpa.c | 3 + include/hw/virtio/virtio-net.h | 8 ++ net/vhost-vdpa.c | 10 +++ 5 files changed, 119 insertions(+), 17 deletions(-) diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c index eccb48ad42..96aa70aea8 100644 --- a/hw/net/virtio-net.c +++ b/hw/net/virtio-net.c @@ -157,6 +157,15 @@ 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) +{ + VirtIONet *n = opaque; + VirtIODevice *vdev = VIRTIO_DEVICE(n); + + n->rx_pkt_cnt = 0; + virtio_notify(vdev, n->vqs[0].rx_vq); +} + static void virtio_net_get_config(VirtIODevice *vdev, uint8_t *config) { VirtIONet *n = VIRTIO_NET(vdev); @@ -1081,6 +1090,29 @@ static int virtio_net_handle_offloads(VirtIONet *n, uint8_t cmd, } } +static int virtio_net_handle_coal(VirtIONet *n, uint8_t cmd, + struct iovec *iov, unsigned int iov_cnt) +{ + struct virtio_net_ctrl_coal coal; + size_t s; + + 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) { + n->rx_coal_usecs = le32_to_cpu(coal.max_usecs); + n->rx_coal_packets = le32_to_cpu(coal.max_packets); + } else if (cmd == VIRTIO_NET_CTRL_NOTF_COAL_TX_SET) { + n->tx_coal_usecs = le32_to_cpu(coal.max_usecs); + n->tx_coal_packets = le32_to_cpu(coal.max_packets); + n->tx_timeout = n->tx_coal_usecs * 1000; + } + + return VIRTIO_NET_OK; +} + static int virtio_net_handle_mac(VirtIONet *n, uint8_t cmd, struct iovec *iov, unsigned int iov_cnt) { @@ -1582,6 +1614,8 @@ 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)); @@ -2041,7 +2075,18 @@ 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 */ + n->rx_pkt_cnt += i; + if (n->rx_coal_usecs == 0 || n->rx_pkt_cnt >= n->rx_coal_packets) { + timer_del(n->rx_index_timer); + virtio_net_rx_notify(n); + } else { + if (n->rx_pkt_cnt == i) { + timer_mod(n->rx_index_timer, + qemu_clock_get_us(QEMU_CLOCK_VIRTUAL) + n->rx_coal_usecs); + } + } return size; @@ -2900,6 +2945,7 @@ static void virtio_net_tx_timer(void *opaque) if (ret == -EBUSY || ret == -EINVAL) { return; } + n->tx_pkt_cnt -= ret; /* * If we flush a full burst of packets, assume there are * more coming and immediately rearm @@ -2919,6 +2965,7 @@ 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); + n->tx_pkt_cnt -= ret; q->tx_waiting = 1; timer_mod(q->tx_timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + n->tx_timeout); @@ -2974,27 +3021,45 @@ static void virtio_net_tx_bh(void *opaque) } } -static void virtio_net_add_queue(VirtIONet *n, int index) +static void virtio_net_handle_tx_dispatch(VirtIODevice *vdev, VirtQueue *vq) { - VirtIODevice *vdev = VIRTIO_DEVICE(n); + VirtIONet *n = VIRTIO_NET(vdev); - n->vqs[index].rx_vq = virtio_add_queue(vdev, n->net_conf.rx_queue_size, - virtio_net_handle_rx); + n->tx_pkt_cnt++; + bool use_timer = n->tx_timer_activate || n->tx_coal_usecs > 0 || + n->tx_coal_packets > 0; - if (n->net_conf.tx && !strcmp(n->net_conf.tx, "timer")) { - n->vqs[index].tx_vq = - virtio_add_queue(vdev, n->net_conf.tx_queue_size, - virtio_net_handle_tx_timer); - n->vqs[index].tx_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, - virtio_net_tx_timer, - &n->vqs[index]); + if (use_timer && n->tx_pkt_cnt < n->tx_coal_packets) { + virtio_net_handle_tx_timer(vdev, vq); } else { - n->vqs[index].tx_vq = - virtio_add_queue(vdev, n->net_conf.tx_queue_size, - virtio_net_handle_tx_bh); - n->vqs[index].tx_bh = qemu_bh_new_guarded(virtio_net_tx_bh, &n->vqs[index], - &DEVICE(vdev)->mem_reentrancy_guard); + n->tx_pkt_cnt = 0; + virtio_net_handle_tx_bh(vdev, vq); } +} + +static void virtio_net_add_queue(VirtIONet *n, int index) +{ + VirtIODevice *vdev = VIRTIO_DEVICE(n); + + n->vqs[index].rx_vq = + virtio_add_queue(vdev, + n->net_conf.rx_queue_size, + virtio_net_handle_rx); + + n->vqs[index].tx_vq = + virtio_add_queue(vdev, + n->net_conf.tx_queue_size, + virtio_net_handle_tx_dispatch); + + n->vqs[index].tx_timer = + timer_new_ns(QEMU_CLOCK_VIRTUAL, + virtio_net_tx_timer, + &n->vqs[index]); + + n->vqs[index].tx_bh = + qemu_bh_new_guarded(virtio_net_tx_bh, + &n->vqs[index], + &DEVICE(vdev)->mem_reentrancy_guard); n->vqs[index].tx_waiting = 0; n->vqs[index].n = n; @@ -3089,6 +3154,7 @@ 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); + virtio_add_feature_ex(features, VIRTIO_NET_F_NOTF_COAL); if (!peer_has_vnet_hdr(n)) { virtio_clear_feature_ex(features, VIRTIO_NET_F_CSUM); @@ -3972,6 +4038,10 @@ static void virtio_net_device_realize(DeviceState *dev, Error **errp) error_printf("Defaulting to \"bh\""); } + if (n->net_conf.tx && strcmp(n->net_conf.tx, "timer")) { + n->tx_timer_activate = true; + } + n->net_conf.tx_queue_size = MIN(virtio_net_max_tx_queue_size(n), n->net_conf.tx_queue_size); @@ -4048,6 +4118,14 @@ static void virtio_net_device_realize(DeviceState *dev, Error **errp) n->rss_data.specified_hash_types.on_bits | n->rss_data.specified_hash_types.auto_bits; } + n->rx_pkt_cnt = 0; + n->tx_pkt_cnt = 0; + n->rx_coal_usecs = 0; + n->tx_coal_usecs = 0; + n->rx_coal_packets = 0; + n->tx_coal_packets = 0; + n->rx_index_timer = timer_new_us(QEMU_CLOCK_VIRTUAL, + virtio_net_rx_notify, n); } static void virtio_net_device_unrealize(DeviceState *dev) @@ -4262,6 +4340,8 @@ 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, true), DEFINE_PROP_ON_OFF_AUTO_BIT64("hash-ipv4", VirtIONet, rss_data.specified_hash_types, VIRTIO_NET_HASH_REPORT_IPv4 - 1, diff --git a/hw/virtio/vhost-shadow-virtqueue.c b/hw/virtio/vhost-shadow-virtqueue.c index 6242aeb69c..104ed0ce8f 100644 --- a/hw/virtio/vhost-shadow-virtqueue.c +++ b/hw/virtio/vhost-shadow-virtqueue.c @@ -37,6 +37,7 @@ bool vhost_svq_valid_features(uint64_t features, Error **errp) case VIRTIO_RING_F_INDIRECT_DESC: continue; + case VIRTIO_F_RING_RESET: case VIRTIO_F_ACCESS_PLATFORM: /* SVQ trust in the host's IOMMU to translate addresses */ case VIRTIO_F_VERSION_1: diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c index 2f8f11df86..8eb9bdb961 100644 --- a/hw/virtio/vhost-vdpa.c +++ b/hw/virtio/vhost-vdpa.c @@ -1541,6 +1541,9 @@ static int vhost_vdpa_get_features(struct vhost_dev *dev, if (ret == 0) { /* Add SVQ logging capabilities */ *features |= BIT_ULL(VHOST_F_LOG_ALL); + + /* Add notification coalescing features */ + *features |= BIT_ULL(VIRTIO_NET_F_NOTF_COAL); } return ret; diff --git a/include/hw/virtio/virtio-net.h b/include/hw/virtio/virtio-net.h index 5b8ab7bda7..024501ed37 100644 --- a/include/hw/virtio/virtio-net.h +++ b/include/hw/virtio/virtio-net.h @@ -231,6 +231,14 @@ struct VirtIONet { struct EBPFRSSContext ebpf_rss; uint32_t nr_ebpf_rss_fds; char **ebpf_rss_fds; + QEMUTimer *rx_index_timer; + uint32_t rx_coal_usecs; + uint32_t rx_coal_packets; + uint32_t rx_pkt_cnt; + uint32_t tx_coal_usecs; + uint32_t tx_coal_packets; + uint32_t tx_pkt_cnt; + bool tx_timer_activate; }; size_t virtio_net_handle_ctrl_iov(VirtIODevice *vdev, diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c index 3df6091274..6a5d0f4cae 100644 --- a/net/vhost-vdpa.c +++ b/net/vhost-vdpa.c @@ -61,6 +61,7 @@ static const int vdpa_feature_bits[] = { VIRTIO_F_NOTIFY_ON_EMPTY, VIRTIO_F_RING_PACKED, VIRTIO_F_RING_RESET, + VIRTIO_F_ORDER_PLATFORM, VIRTIO_F_VERSION_1, VIRTIO_F_IN_ORDER, VIRTIO_F_NOTIFICATION_DATA, @@ -70,6 +71,8 @@ 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_GUEST_ANNOUNCE, + VIRTIO_NET_F_NOTF_COAL, VIRTIO_NET_F_CTRL_VQ, VIRTIO_NET_F_GSO, VIRTIO_NET_F_GUEST_CSUM, @@ -115,6 +118,13 @@ static const uint64_t vdpa_svq_device_features = BIT_ULL(VIRTIO_NET_F_HOST_UFO) | BIT_ULL(VIRTIO_NET_F_MRG_RXBUF) | BIT_ULL(VIRTIO_NET_F_STATUS) | + BIT_ULL(VIRTIO_F_RING_RESET) | + BIT_ULL(VIRTIO_F_ORDER_PLATFORM) | + BIT_ULL(VIRTIO_NET_F_GUEST_USO4) | + BIT_ULL(VIRTIO_NET_F_GUEST_USO6) | + BIT_ULL(VIRTIO_NET_F_HOST_USO) | + BIT_ULL(VIRTIO_NET_F_GUEST_ANNOUNCE) | + BIT_ULL(VIRTIO_NET_F_NOTF_COAL) | BIT_ULL(VIRTIO_NET_F_CTRL_VQ) | BIT_ULL(VIRTIO_NET_F_GSO) | BIT_ULL(VIRTIO_NET_F_CTRL_RX) | -- 2.53.0
