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From 09fdcd8662d3153e6c4c68864edc89b5f39ae169 Mon Sep 17 00:00:00 2001
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Message-Id: <09fdcd8662d3153e6c4c68864edc89b5f39ae169@dist-git>
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From: Michal Privoznik <mprivozn@redhat.com>
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Date: Tue, 18 Feb 2014 11:50:32 +0100
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Subject: [PATCH] qemuBuildNicDevStr: Set vectors= on Multiqueue
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https://bugzilla.redhat.com/show_bug.cgi?id=1066209
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Yet another advice appeared on the Multiqueue wiki page:
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http://www.linux-kvm.org/page/Multiqueue#Enable_MQ_feature
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We should add vectors=N onto the qemu command line, where
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N = 2 * (number of queues) + 1.
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(cherry picked from commit 4f588a1b465e2b32c78429e8d2f2c010eb11da19)
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Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
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Conflicts:
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	src/qemu/qemu_command.c: Context as 54a77c6d is not backported yet
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Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
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---
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 src/qemu/qemu_command.c | 13 +++++++------
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 src/qemu/qemu_command.h |  2 +-
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 src/qemu/qemu_hotplug.c |  4 +---
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 3 files changed, 9 insertions(+), 10 deletions(-)
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diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
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index b5729a4..e6a6650 100644
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--- a/src/qemu/qemu_command.c
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+++ b/src/qemu/qemu_command.c
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@@ -4811,7 +4811,7 @@ qemuBuildNicDevStr(virDomainDefPtr def,
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                    virDomainNetDefPtr net,
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                    int vlan,
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                    int bootindex,
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-                   bool multiqueue,
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+                   int vhostfdSize,
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                    virQEMUCapsPtr qemuCaps)
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 {
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     virBuffer buf = VIR_BUFFER_INITIALIZER;
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@@ -4864,8 +4864,11 @@ qemuBuildNicDevStr(virDomainDefPtr def,
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                               virDomainVirtioEventIdxTypeToString(net->driver.virtio.event_idx));
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         }
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     }
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-    if (usingVirtio && multiqueue)
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-        virBufferAddLit(&buf, ",mq=on");
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+    if (usingVirtio && vhostfdSize > 1) {
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+        /* As advised at http://www.linux-kvm.org/page/Multiqueue
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+         * we should add vectors=2*N+1 where N is the vhostfdSize */
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+        virBufferAsprintf(&buf, ",mq=on,vectors=%d", 2 * vhostfdSize + 1);
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+    }
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     if (vlan == -1)
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         virBufferAsprintf(&buf, ",netdev=host%s", net->info.alias);
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     else
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@@ -7407,10 +7410,8 @@ qemuBuildInterfaceCommandLine(virCommandPtr cmd,
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         virCommandAddArgList(cmd, "-netdev", host, NULL);
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     }
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     if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE)) {
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-        bool multiqueue = tapfdSize > 1 || vhostfdSize > 1;
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-
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         if (!(nic = qemuBuildNicDevStr(def, net, vlan, bootindex,
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-                                       multiqueue, qemuCaps)))
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+                                       vhostfdSize, qemuCaps)))
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             goto cleanup;
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         virCommandAddArgList(cmd, "-device", nic, NULL);
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     } else {
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diff --git a/src/qemu/qemu_command.h b/src/qemu/qemu_command.h
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index 39da555..06c4b30 100644
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--- a/src/qemu/qemu_command.h
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+++ b/src/qemu/qemu_command.h
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@@ -106,7 +106,7 @@ char * qemuBuildNicDevStr(virDomainDefPtr def,
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                           virDomainNetDefPtr net,
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                           int vlan,
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                           int bootindex,
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-                          bool multiqueue,
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+                          int vhostfdSize,
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                           virQEMUCapsPtr qemuCaps);
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 char *qemuDeviceDriveHostAlias(virDomainDiskDefPtr disk,
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diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c
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index d9ce951..a3c291d 100644
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--- a/src/qemu/qemu_hotplug.c
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+++ b/src/qemu/qemu_hotplug.c
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@@ -859,10 +859,8 @@ int qemuDomainAttachNetDevice(virConnectPtr conn,
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     }
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     if (virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_DEVICE)) {
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-        bool multiqueue = tapfdSize > 1 || vhostfdSize > 1;
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-
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         if (!(nicstr = qemuBuildNicDevStr(vm->def, net, vlan, 0,
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-                                          multiqueue, priv->qemuCaps)))
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+                                          vhostfdSize, priv->qemuCaps)))
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             goto try_remove;
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     } else {
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         if (!(nicstr = qemuBuildNicStr(net, NULL, vlan)))
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-- 
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1.9.0
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