From 1f8a488376ae7c9132937bde5bda1646d272545a Mon Sep 17 00:00:00 2001 From: Xiao Wang Date: Fri, 12 Aug 2016 01:38:49 +0200 Subject: [PATCH 14/17] virtio-net: allow increasing rx queue size RH-Author: Xiao Wang Message-id: <1470965929-5454-1-git-send-email-jasowang@redhat.com> Patchwork-id: 71953 O-Subject: [RHEL7.3/7.2z qemu-kvm-rhev PATCH] virtio-net: allow increasing rx queue size Bugzilla: 1358962 RH-Acked-by: Thomas Huth RH-Acked-by: Maxime Coquelin RH-Acked-by: Miroslav Rezanina From: "Michael S. Tsirkin" Bugzilla: 1358962 Upstream: Queued in my tree for 2.8 Brew Build: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=11553930 Test status: Smoking test by myself This allows increasing the rx queue size up to 1024: unlike with tx, guests don't put in huge S/G lists into RX so the risk of running into the max 1024 limitation due to some off-by-one seems small. It's helpful for users like OVS-DPDK which don't do any buffering on the host - 1K roughly matches 500 entries in tun + 256 in the current rx queue, which seems to work reasonably well. We could probably make do with ~750 entries but virtio spec limits us to powers of two. It might be a good idea to specify an s/g size limit in a future version. It also might be possible to make the queue size smaller down the road, 64 seems like the minimal value which will still work (as guests seem to assume a queue full of 1.5K buffers is enough to process the largest incoming packet, which is ~64K). No one actually asked for this, and with virtio 1 guests can reduce ring size without need for host configuration, so don't bother with this for now. Cc: Cornelia Huck Cc: Jason Wang Suggested-by: Patrik Hermansson Signed-off-by: Michael S. Tsirkin Signed-off-by: Jason Wang Signed-off-by: Miroslav Rezanina --- hw/net/virtio-net.c | 26 +++++++++++++++++++++++++- include/hw/virtio/virtio-net.h | 1 + 2 files changed, 26 insertions(+), 1 deletion(-) diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c index 5798f87..13ab491 100644 --- a/hw/net/virtio-net.c +++ b/hw/net/virtio-net.c @@ -31,6 +31,11 @@ #define MAC_TABLE_ENTRIES 64 #define MAX_VLAN (1 << 12) /* Per 802.1Q definition */ +/* previously fixed value */ +#define VIRTIO_NET_RX_QUEUE_DEFAULT_SIZE 256 +/* for now, only allow larger queues; with virtio-1, guest can downsize */ +#define VIRTIO_NET_RX_QUEUE_MIN_SIZE VIRTIO_NET_RX_QUEUE_DEFAULT_SIZE + /* * Calculate the number of bytes up to and including the given 'field' of * 'container'. @@ -1412,7 +1417,8 @@ static void virtio_net_add_queue(VirtIONet *n, int index) { VirtIODevice *vdev = VIRTIO_DEVICE(n); - n->vqs[index].rx_vq = virtio_add_queue(vdev, 256, virtio_net_handle_rx); + n->vqs[index].rx_vq = virtio_add_queue(vdev, n->net_conf.rx_queue_size, + virtio_net_handle_rx); if (n->net_conf.tx && !strcmp(n->net_conf.tx, "timer")) { n->vqs[index].tx_vq = virtio_add_queue(vdev, 256, virtio_net_handle_tx_timer); @@ -1748,6 +1754,22 @@ static void virtio_net_device_realize(DeviceState *dev, Error **errp) virtio_net_set_config_size(n, n->host_features); virtio_init(vdev, "virtio-net", VIRTIO_ID_NET, n->config_size); + /* + * We set a lower limit on RX queue size to what it always was. + * Guests that want a smaller ring can always resize it without + * help from us (using virtio 1 and up). + */ + if (n->net_conf.rx_queue_size < VIRTIO_NET_RX_QUEUE_MIN_SIZE || + n->net_conf.rx_queue_size > VIRTQUEUE_MAX_SIZE || + (n->net_conf.rx_queue_size & (n->net_conf.rx_queue_size - 1))) { + error_setg(errp, "Invalid rx_queue_size (= %" PRIu16 "), " + "must be a power of 2 between %d and %d.", + n->net_conf.rx_queue_size, VIRTIO_NET_RX_QUEUE_MIN_SIZE, + VIRTQUEUE_MAX_SIZE); + virtio_cleanup(vdev); + return; + } + n->max_queues = MAX(n->nic_conf.peers.queues, 1); if (n->max_queues * 2 + 1 > VIRTIO_QUEUE_MAX) { error_setg(errp, "Invalid number of queues (= %" PRIu32 "), " @@ -1909,6 +1931,8 @@ static Property virtio_net_properties[] = { TX_TIMER_INTERVAL), DEFINE_PROP_INT32("x-txburst", VirtIONet, net_conf.txburst, TX_BURST), DEFINE_PROP_STRING("tx", VirtIONet, net_conf.tx), + DEFINE_PROP_UINT16("rx_queue_size", VirtIONet, net_conf.rx_queue_size, + VIRTIO_NET_RX_QUEUE_DEFAULT_SIZE), DEFINE_PROP_END_OF_LIST(), }; diff --git a/include/hw/virtio/virtio-net.h b/include/hw/virtio/virtio-net.h index 0cabdb6..268f7e1 100644 --- a/include/hw/virtio/virtio-net.h +++ b/include/hw/virtio/virtio-net.h @@ -35,6 +35,7 @@ typedef struct virtio_net_conf uint32_t txtimer; int32_t txburst; char *tx; + uint16_t rx_queue_size; } virtio_net_conf; /* Maximum packet size we can receive from tap device: header + 64k */ -- 1.8.3.1