merge_buffers: Add option to disable merge buffer on qemu startup

In cases with VHost user and non-jumbo frame scenarios we can
disable merge buffers on the guest NICS to improve performance.
This patch adds this option to the 04_vnf conf file.

JIRA: VSPERF-388

Change-Id: Ic1f776e90fdccaa5d5a0c952c96811a8747fe936
Signed-off-by: Christian Trautman <ctrautma@redhat.com>

diff --git a/conf/04_vnf.conf b/conf/04_vnf.conf
index 2e86b35..ac5559a 100644 (file)
--- a/conf/04_vnf.conf
+++ b/conf/04_vnf.conf
@@ -140,11 +140,15 @@ GUEST_CORE_BINDING = [('#EVAL(6+2*#VMINDEX)', '#EVAL(7+2*#VMINDEX)')]
 # using Vanilla OVS without enabling switch multi-queue.
 GUEST_NIC_QUEUES = [0]
 
+# Disable VHost user guest NIC merge buffers by enabling the below setting. This
+# can improve performance when not using Jumbo Frames.
+GUEST_NIC_MERGE_BUFFERS_DISABLE = [True]
+
 # Virtio-Net vhost thread CPU mapping. If using  vanilla OVS with virtio-net,
 # you can affinitize the vhost-net threads by enabling the below setting. There
 # is one vhost-net thread per port per queue so one guest with 2 queues will
 # have 4 vhost-net threads. If more threads are present than CPUs given, the
-# affinitize will overlap CPUs.
+# affinitize will overlap CPUs in a round robin fashion.
 VSWITCH_VHOST_NET_AFFINITIZATION = False
 VSWITCH_VHOST_CPU_MAP = [4,5,8,11]
 

diff --git a/vnfs/qemu/qemu_dpdk_vhost_user.py b/vnfs/qemu/qemu_dpdk_vhost_user.py
index fc46aba..794a477 100644 (file)
--- a/vnfs/qemu/qemu_dpdk_vhost_user.py
+++ b/vnfs/qemu/qemu_dpdk_vhost_user.py
@@ -39,6 +39,12 @@ class QemuDpdkVhostUser(IVnfQemu):
         else:
             queue_str, mq_vector_str = '', ''
 
+        # Guest merge buffer setting
+        if S.getValue('GUEST_NIC_MERGE_BUFFERS_DISABLE')[self._number]:
+            merge_buff = 'mrg_rxbuf=off,'
+        else:
+            merge_buff = ''
+
         # calculate index of first interface, i.e. check how many
         # interfaces has been created for previous VMs, where 1st NIC
         # of 1st VM has index 0
@@ -60,7 +66,8 @@ class QemuDpdkVhostUser(IVnfQemu):
                           '-device',
                           'virtio-net-pci,mac=' +
                           self._nics[nic]['mac'] +
-                          ',netdev=' + net + ',csum=off,gso=off,' +
+                          ',netdev=' + net + ',csum=off,' + merge_buff +
+                          'gso=off,' +
                           'guest_tso4=off,guest_tso6=off,guest_ecn=off' +
                           mq_vector_str,
                          ]