xenapi: max out VCPU count

Give as much VCPUs to the DevStack machine as possible. First asking
xenapi about its CPU count, and as a fallback, count the CPUs in dom0.
This should result in faster test runs.

Change-Id: I1ffb99ecd435f1d7eb5754fe9cd99f0e8ceae6dc

tools/xen/functions

@@ -287,3 +287,35 @@ function set_vm_memory() {
         dynamic-max=${memory}MiB \
         uuid=$vm
 }
+
+function max_vcpus() {
+    local vm_name_label
+
+    vm_name_label="$1"
+
+    local vm
+    local host
+    local cpu_count
+
+    host=$(xe host-list --minimal)
+    vm=$(_vm_uuid "$vm_name_label")
+
+    cpu_count=$(xe host-param-get \
+        param-name=cpu_info \
+        uuid=$host |
+        sed -e 's/^.*cpu_count: \([0-9]*\);.*$/\1/g')
+
+    if [ -z "$cpu_count" ]; then
+        # get dom0's vcpu count
+        cpu_count=$(cat /proc/cpuinfo | grep processor | wc -l)
+    fi
+
+    # Assert cpu_count is not empty
+    [ -n "$cpu_count" ]
+
+    # Assert ithas a numeric nonzero value
+    expr "$cpu_count" + 0
+
+    xe vm-param-set uuid=$vm VCPUs-max=$cpu_count
+    xe vm-param-set uuid=$vm VCPUs-at-startup=$cpu_count
+}

tools/xen/install_os_domU.sh

@@ -263,6 +263,9 @@ $THIS_DIR/prepare_guest_template.sh "$GUEST_NAME"
 # Set virtual machine parameters
 set_vm_memory "$GUEST_NAME" "$OSDOMU_MEM_MB"
 
+# Max out VCPU count for better performance
+max_vcpus "$GUEST_NAME"
+
 # start the VM to run the prepare steps
 xe vm-start vm="$GUEST_NAME"