guest->host host->guest || cpu utilization throughput vmexits || 01-tx-notifies-disabled-for-longer 02-flush-in-io-thread 03-catch-more-io 04-no-tx-timer 05-drop-mutex
From: Mark McLoughlinIf you're interested, the nasty scripts I used to generate these are hereSubject: [PATCH] kvm: qemu: virtio_net: don't flush the tx queue from the vcpu thread If we have already set up a tx timer and disabled notifies but we still get a notify, the queue must be full and we should flush ASAP. Signal a flush from the I/O thread using a bottom half so that we don't pause the guest by flushing in the vcpu thread. Signed-off-by: Mark McLoughlin --- qemu/hw/virtio-net.c | 20 +++++++++++++++++++- 1 files changed, 19 insertions(+), 1 deletions(-) diff --git a/qemu/hw/virtio-net.c b/qemu/hw/virtio-net.c index e816041..2d5f712 100644 --- a/qemu/hw/virtio-net.c +++ b/qemu/hw/virtio-net.c @@ -70,6 +70,8 @@ typedef struct VirtIONet VLANClientState *vc; QEMUTimer *tx_timer; int tx_timer_active; + QEMUBH *tx_bh; + int tx_bh_scheduled; } VirtIONet; /* TODO @@ -268,10 +270,14 @@ static void virtio_net_handle_tx(VirtIODevice *vdev, VirtQueue *vq) { VirtIONet *n = to_virtio_net(vdev); + if (n->tx_bh_scheduled) + return; + if (n->tx_timer_active) { qemu_del_timer(n->tx_timer); n->tx_timer_active = 0; - virtio_net_flush_tx(n, n->tx_vq, 1); + qemu_bh_schedule(n->tx_bh); + n->tx_bh_scheduled = 1; } else { qemu_mod_timer(n->tx_timer, qemu_get_clock(vm_clock) + TX_TIMER_INTERVAL); @@ -289,6 +295,15 @@ static void virtio_net_tx_timer(void *opaque) virtio_net_flush_tx(n, n->tx_vq, 1); } +static void virtio_net_tx_bh(void *opaque) +{ + VirtIONet *n = opaque; + + n->tx_bh_scheduled = 0; + + virtio_net_flush_tx(n, n->tx_vq, 1); +} + static void virtio_net_save(QEMUFile *f, void *opaque) { VirtIONet *n = opaque; @@ -325,6 +340,7 @@ static int virtio_net_uninit(PCIDevice *dev) qemu_del_timer(n->tx_timer); qemu_free_timer(n->tx_timer); + qemu_bh_delete(n->tx_bh); return 0; } @@ -352,6 +368,8 @@ PCIDevice *virtio_net_init(PCIBus *bus, NICInfo *nd, int devfn) 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->vdev.pci_dev.unregister = virtio_net_uninit; -- 1.6.0.1