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authorAlex Williamson <alex.williamson@redhat.com>2010-09-02 09:01:10 -0600
committerMichael S. Tsirkin <mst@redhat.com>2010-09-07 20:29:29 +0300
commita697a334b3c4d3250e6420f5d38550ea10eb5319 (patch)
treef22a82803a21178bb158a63fe9647a7155d25693 /hw/virtio-pci.c
parent4b4b8d361c21209bd6414c369fe93eb70c5ff50d (diff)
virtio-net: Introduce a new bottom half packet TX
Based on a patch from Mark McLoughlin, this patch introduces a new bottom half packet transmitter that avoids the latency imposed by the tx_timer approach. Rather than scheduling a timer when a TX packet comes in, schedule a bottom half to be run from the iothread. The bottom half handler first attempts to flush the queue with notification disabled (this is where we could race with a guest without txburst). If we flush a full burst, reschedule immediately. If we send short of a full burst, try to re-enable notification. To avoid a race with TXs that may have occurred, we must then flush again. If we find some packets to send, the guest it probably active, so we can reschedule again. tx_timer and tx_bh are mutually exclusive, so we can re-use the tx_waiting flag to indicate one or the other needs to be setup. This allows us to seamlessly migrate between timer and bh TX handling. The bottom half handler becomes the new default and we add a new tx= option to virtio-net-pci. Usage: -device virtio-net-pci,tx=timer # select timer mitigation vs "bh" Signed-off-by: Alex Williamson <alex.williamson@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Diffstat (limited to 'hw/virtio-pci.c')
-rw-r--r--hw/virtio-pci.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
index 3a5b3e6b23..86e6b0a561 100644
--- a/hw/virtio-pci.c
+++ b/hw/virtio-pci.c
@@ -695,6 +695,7 @@ static PCIDeviceInfo virtio_info[] = {
net.txtimer, TX_TIMER_INTERVAL),
DEFINE_PROP_INT32("x-txburst", VirtIOPCIProxy,
net.txburst, TX_BURST),
+ DEFINE_PROP_STRING("tx", VirtIOPCIProxy, net.tx),
DEFINE_PROP_END_OF_LIST(),
},
.qdev.reset = virtio_pci_reset,