On Fri, Aug 14, 2009 at 03:50:16PM -0400, Gregory Haskins wrote: > Gregory Haskins wrote: > > Anthony Liguori wrote: > >> Gregory Haskins wrote: > >>> I re-ran the numbers on 10GE against the actual alacrityvm v0.1 release > >>> available in git on kernel.org. > >>> > >>> I tried to include the newly announced "vhost" driver (Michael Tsirkin) > >>> for virtio acceleration, but ran into issues getting the patches to > >>> apply. > >>> > >>> For now, this includes native, virtio-u (virtio-userspace), and venet > >>> all running on 31-rc4. If I can resolve the issue with Michaels > >>> patches, I will add "virtio-k" (virtio-kernel) to the mix as well. For > >>> now, here are the results for 1500mtu: > >>> > >>> native: 7388Mb/s, 29.8us rtt (33505 tps udp-rr) > >>> venet: 3654Mb/s, 56.8us rtt (17600 tps udp-rr) > >>> virtio-u: 1955Mb/s, 4016.0us rtt ( 249 tps udp-rr) > >>> > > I re-ran the numbers now that I have the HRT issue straighted out. > Native and virtio stayed level, venet recovered from the 3.6Gb/s > quagmire it was in, back up to ~4.5Gb/s. > > native (hw): 7388Mb/s, 29.8us rtt (33500 tps udp-rr) > venet (alacrityvm): 4560Mb/s, 56.8us rtt (17600 tps udp-rr) > virtio-u (kvm): 2670Mb/s, 265.7us rtt ( 3764 tps udp-rr) > virtio-k (kvm): d-n-f > > (still having problems getting vhost to run). Will try again next week.) > > I have updated the graphs on the wiki: > > http://developer.novell.com/wiki/index.php/AlacrityVM > > Have a nice weekend, all. > > -Greg > > Hi Greg, could you check what does disabling tx timer completely do to virtio-u performance? Here's a patch from Mark McLoughlin do this this: it works and seems to improve latency for me. From: Mark McLoughlin <markmc@xxxxxxxxxx> Subject: virtio_net: remove the tx mitigation timer The tx mitigation timer is designed to reduce the rate of guest exits thereby improving throughput. However, we have identified a number of cases where mitigation hurts throughput and benchmarking has shown that it only helps throughput in a very limited number of cases. This patch firstly removes the timer and replaces it with a bottom half. When the host is notified of a packet on the tx queue, it schedules a bottom half in the I/O thread in order to flush the queue. Next, it disables enabling notifications until it has flushed the queue. In order to avoid a race condition with this, it flushes the queue a second time when notifications are re-enabled. Finally, if it successfully flushed a number of packets in the bottom half, it disables notifications re-schedules the bottom half to quickly flush the queue again. Migration is handled by equating the tx_timer_active savevm field to tx_bh_scheduled. Signed-off-by: Mark McLoughlin <markmc@xxxxxxxxxx> --- diff --git a/hw/virtio-net.c b/hw/virtio-net.c index 95d9f93..835f4e1 100644 --- a/hw/virtio-net.c +++ b/hw/virtio-net.c @@ -37,8 +37,8 @@ typedef struct VirtIONet VirtQueue *tx_vq; VirtQueue *ctrl_vq; VLANClientState *vc; - QEMUTimer *tx_timer; - int tx_timer_active; + QEMUBH *tx_bh; + int tx_bh_scheduled; struct { VirtQueueElement elem; ssize_t len; @@ -591,7 +591,7 @@ static ssize_t virtio_net_receive2(VLANClientState *vc, const uint8_t *buf, size return size; } -static void virtio_net_flush_tx(VirtIONet *n, VirtQueue *vq); +static int virtio_net_flush_tx(VirtIONet *n, VirtQueue *vq, int enable_notify); static void virtio_net_tx_complete(VLANClientState *vc, ssize_t len) { @@ -603,7 +603,7 @@ static void virtio_net_tx_complete(VLANClientState *vc, ssize_t len) n->async_tx.elem.out_num = n->async_tx.len = 0; virtio_queue_set_notification(n->tx_vq, 1); - virtio_net_flush_tx(n, n->tx_vq); + virtio_net_flush_tx(n, n->tx_vq, 0); } static ssize_t virtio_net_receive(VLANClientState *vc, const uint8_t *buf, size_t size) @@ -617,9 +617,10 @@ static ssize_t virtio_net_receive_raw(VLANClientState *vc, const uint8_t *buf, s } /* TX */ -static void virtio_net_flush_tx(VirtIONet *n, VirtQueue *vq) +static int virtio_net_flush_tx(VirtIONet *n, VirtQueue *vq, int enable_notify) { VirtQueueElement elem; + int num_packets = 0; #ifdef TAP_VNET_HDR int has_vnet_hdr = tap_has_vnet_hdr(n->vc->vlan->first_client); #else @@ -629,11 +630,11 @@ static void virtio_net_flush_tx(VirtIONet *n, VirtQueue *vq) return; if (!(n->vdev.status & VIRTIO_CONFIG_S_DRIVER_OK)) - return; + return num_packets; if (n->async_tx.elem.out_num) { virtio_queue_set_notification(n->tx_vq, 0); - return; + return num_packets; } while (virtqueue_pop(vq, &elem)) { @@ -670,45 +671,48 @@ static void virtio_net_flush_tx(VirtIONet *n, VirtQueue *vq) virtio_queue_set_notification(n->tx_vq, 0); n->async_tx.elem = elem; n->async_tx.len = len; - return; + return num_packets; } len += ret; virtqueue_push(vq, &elem, len); virtio_notify(&n->vdev, vq); + + num_packets++; + } + + if (enable_notify) { + virtio_queue_set_notification(vq, 1); + num_packets += virtio_net_flush_tx(n, vq, 0); } + + return num_packets; } static void virtio_net_handle_tx(VirtIODevice *vdev, VirtQueue *vq) { VirtIONet *n = to_virtio_net(vdev); - if (n->tx_timer_active) { - virtio_queue_set_notification(vq, 1); - qemu_del_timer(n->tx_timer); - n->tx_timer_active = 0; - virtio_net_flush_tx(n, vq); - } else { - qemu_mod_timer(n->tx_timer, - qemu_get_clock(vm_clock) + TX_TIMER_INTERVAL); - n->tx_timer_active = 1; - virtio_queue_set_notification(vq, 0); - } + if (n->tx_bh_scheduled) + return; + + virtio_queue_set_notification(n->tx_vq, 0); + qemu_bh_schedule(n->tx_bh); + n->tx_bh_scheduled = 1; } -static void virtio_net_tx_timer(void *opaque) +static void virtio_net_tx_bh(void *opaque) { VirtIONet *n = opaque; - n->tx_timer_active = 0; - - /* Just in case the driver is not ready on more */ - if (!(n->vdev.status & VIRTIO_CONFIG_S_DRIVER_OK)) - return; + n->tx_bh_scheduled = 0; - virtio_queue_set_notification(n->tx_vq, 1); - virtio_net_flush_tx(n, n->tx_vq); + if (virtio_net_flush_tx(n, n->tx_vq, 1)) { + virtio_queue_set_notification(n->tx_vq, 0); + qemu_bh_schedule(n->tx_bh); + n->tx_bh_scheduled = 1; + } } static void virtio_net_save(QEMUFile *f, void *opaque) @@ -718,7 +722,7 @@ static void virtio_net_save(QEMUFile *f, void *opaque) virtio_save(&n->vdev, f); qemu_put_buffer(f, n->mac, ETH_ALEN); - qemu_put_be32(f, n->tx_timer_active); + qemu_put_be32(f, n->tx_bh_scheduled); qemu_put_be32(f, n->mergeable_rx_bufs); qemu_put_be16(f, n->status); qemu_put_byte(f, n->promisc); @@ -752,7 +756,7 @@ static int virtio_net_load(QEMUFile *f, void *opaque, int version_id) virtio_load(&n->vdev, f); qemu_get_buffer(f, n->mac, ETH_ALEN); - n->tx_timer_active = qemu_get_be32(f); + n->tx_bh_scheduled = qemu_get_be32(f); n->mergeable_rx_bufs = qemu_get_be32(f); if (version_id >= 3) @@ -814,9 +818,8 @@ static int virtio_net_load(QEMUFile *f, void *opaque, int version_id) } n->mac_table.first_multi = i; - if (n->tx_timer_active) { - qemu_mod_timer(n->tx_timer, - qemu_get_clock(vm_clock) + TX_TIMER_INTERVAL); + if (n->tx_bh_scheduled) { + qemu_bh_schedule(n->tx_bh); } return 0; @@ -833,9 +836,6 @@ static void virtio_net_cleanup(VLANClientState *vc) qemu_free(n->mac_table.macs); qemu_free(n->vlans); - qemu_del_timer(n->tx_timer); - qemu_free_timer(n->tx_timer); - virtio_cleanup(&n->vdev); } @@ -881,8 +881,8 @@ VirtIODevice *virtio_net_init(DeviceState *dev) qemu_format_nic_info_str(n->vc, n->mac); - n->tx_timer = qemu_new_timer(vm_clock, virtio_net_tx_timer, n); - n->tx_timer_active = 0; + n->tx_bh = qemu_bh_new(virtio_net_tx_bh, n); + n->tx_bh_scheduled = 0; n->mergeable_rx_bufs = 0; n->promisc = 1; /* for compatibility */ diff --git a/hw/virtio-net.h b/hw/virtio-net.h index 2085181..add7815 100644 --- a/hw/virtio-net.h +++ b/hw/virtio-net.h @@ -47,8 +47,6 @@ #define VIRTIO_NET_S_LINK_UP 1 /* Link is up */ -#define TX_TIMER_INTERVAL 150000 /* 150 us */ - /* Maximum packet size we can receive from tap device: header + 64k */ #define VIRTIO_NET_MAX_BUFSIZE (sizeof(struct virtio_net_hdr) + (64 << 10)) -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
