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| author | Paolo Bonzini <pbonzini@redhat.com> | 2017-01-11 09:38:15 +0100 |
|---|---|---|
| committer | Michael S. Tsirkin <mst@redhat.com> | 2017-01-18 22:59:53 +0200 |
| commit | 4a3f03ba8dbf53fce36d0c1dd5d0cc0f340fe5f3 (patch) | |
| tree | 73d33b70660c43ee052d97ecdfc02aecb4bfce36 | |
| parent | 23eb9e6b6d5315171cc15969bbc755f258004df0 (diff) | |
| download | qemu-4a3f03ba8dbf53fce36d0c1dd5d0cc0f340fe5f3.zip qemu-4a3f03ba8dbf53fce36d0c1dd5d0cc0f340fe5f3.tar.gz qemu-4a3f03ba8dbf53fce36d0c1dd5d0cc0f340fe5f3.tar.bz2 | |
virtio-net: enable ioeventfd even if vhost=off
virtio-net-pci does not enable ioeventfd for historical reasons (and
nobody ever checked whether it should be revisited). Note that other
backends do enable ioeventfd for virtio-net.
However, it has a major effect on performance. On Windows, throughput is
_multiplied_ by 2 or 3 on TCP_STREAM (on small packets it is "only" a 30%
improvement) and a little less so on TCP_MAERTS albeit still very much
statistically significant. Latency also has a single digit improvement.
This is not visible when using vhost, which forces ioeventfd=on, but it
is substantial without vhost. In addition, also on Windows and with the
RHEL 7.3 kernel, APICv seems to slow down virtio-net performance a bit,
but the penalty with this patch goes from -25% to -7%.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
| -rw-r--r-- | hw/virtio/virtio-pci.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c index 854b8f2..8baaf2b 100644 --- a/hw/virtio/virtio-pci.c +++ b/hw/virtio/virtio-pci.c @@ -2278,7 +2278,7 @@ static const TypeInfo virtio_serial_pci_info = { static Property virtio_net_properties[] = { DEFINE_PROP_BIT("ioeventfd", VirtIOPCIProxy, flags, - VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT, false), + VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT, true), DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors, 3), DEFINE_PROP_END_OF_LIST(), }; |