[libvirt] [PATCH] qemuBuildNicDevStr: Set vectors= on Multiqueue
Yet another advice appeared on the Multiqueue wiki page:
http://www.linux-kvm.org/page/Multiqueue#Enable_MQ_feature
We should add vectors=N onto the qemu command line, where
N = 2 * (number of queues) + 1.
Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com>
---
src/qemu/qemu_command.c | 13 +++++++------
src/qemu/qemu_command.h | 2 +-
src/qemu/qemu_hotplug.c | 4 +---
3 files changed, 9 insertions(+), 10 deletions(-)
diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index b5ac15a..dbfa0dc 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -4730,7 +4730,7 @@ qemuBuildNicDevStr(virDomainDefPtr def,
virDomainNetDefPtr net,
int vlan,
int bootindex,
- bool multiqueue,
+ int vhostfdSize,
virQEMUCapsPtr qemuCaps)
{
virBuffer buf = VIR_BUFFER_INITIALIZER;
@@ -4783,8 +4783,11 @@ qemuBuildNicDevStr(virDomainDefPtr def,
virDomainVirtioEventIdxTypeToString(net->driver.virtio.event_idx));
}
}
- if (usingVirtio && multiqueue)
- virBufferAddLit(&buf, ",mq=on");
+ if (usingVirtio && vhostfdSize > 1) {
+ /* As advised at http://www.linux-kvm.org/page/Multiqueue
+ * we should add vectors=2*N+1 where N is the vhostfdSize */
+ virBufferAsprintf(&buf, ",mq=on,vectors=%d", 2 * vhostfdSize + 1);
+ }
if (vlan == -1)
virBufferAsprintf(&buf, ",netdev=host%s", net->info.alias);
else
@@ -7278,10 +7281,8 @@ qemuBuildInterfaceCommandLine(virCommandPtr cmd,
virCommandAddArgList(cmd, "-netdev", host, NULL);
}
if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE)) {
- bool multiqueue = tapfdSize > 1 || vhostfdSize > 1;
-
if (!(nic = qemuBuildNicDevStr(def, net, vlan, bootindex,
- multiqueue, qemuCaps)))
+ vhostfdSize, qemuCaps)))
goto cleanup;
virCommandAddArgList(cmd, "-device", nic, NULL);
} else {
diff --git a/src/qemu/qemu_command.h b/src/qemu/qemu_command.h
index a9854a3..4761705 100644
--- a/src/qemu/qemu_command.h
+++ b/src/qemu/qemu_command.h
@@ -102,7 +102,7 @@ char * qemuBuildNicDevStr(virDomainDefPtr def,
virDomainNetDefPtr net,
int vlan,
int bootindex,
- bool multiqueue,
+ int vhostfdSize,
virQEMUCapsPtr qemuCaps);
char *qemuDeviceDriveHostAlias(virDomainDiskDefPtr disk,
diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c
index 9727410..3491fd6 100644
--- a/src/qemu/qemu_hotplug.c
+++ b/src/qemu/qemu_hotplug.c
@@ -859,10 +859,8 @@ int qemuDomainAttachNetDevice(virConnectPtr conn,
}
if (virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_DEVICE)) {
- bool multiqueue = tapfdSize > 1 || vhostfdSize > 1;
-
if (!(nicstr = qemuBuildNicDevStr(vm->def, net, vlan, 0,
- multiqueue, priv->qemuCaps)))
+ vhostfdSize, priv->qemuCaps)))
goto try_remove;
} else {
if (!(nicstr = qemuBuildNicStr(net, NULL, vlan)))
--
1.8.1.5