qemu: introduce period/quota tuning for emulator

This patch introduces support of setting emulator's period and
quota to limit cpu bandwidth when the vm starts.  Also updates
XML Schema for new entries and docs.

docs/formatdomain.html.in

@@ -388,6 +388,8 @@
     <shares>2048</shares>
     <period>1000000</period>
     <quota>-1</quota>
+    <emulator_period>1000000</period>
+    <emulator_quota>-1</quota>
   </cputune>
   ...
 </domain>
@@ -451,6 +453,28 @@
         <span class="since">Only QEMU driver support since 0.9.4, LXC since
         0.9.10</span>
       </dd>
+
+      <dt><code>emulator_period</code></dt>
+      <dd>
+        The optional <code>emulator_period</code> element specifies the enforcement
+        interval(unit: microseconds). Within <code>emulator_period</code>, emulator
+        threads(those excluding vcpus) of the domain will not be allowed to consume
+        more than <code>emulator_quota</code> worth of runtime. The value should be
+        in range [1000, 1000000]. A period with value 0 means no value.
+        <span class="since">Only QEMU driver support since 0.10.0</span>
+      </dd>
+      <dt><code>emulator_quota</code></dt>
+      <dd>
+        The optional <code>emulator_quota</code> element specifies the maximum
+        allowed bandwidth(unit: microseconds) for domain's emulator threads(those
+        excluding vcpus). A domain with <code>emulator_quota</code> as any negative
+        value indicates that the domain has infinite bandwidth for emulator threads
+        (those excluding vcpus), which means that it is not bandwidth controlled.
+        The value should be in range [1000, 18446744073709551] or less than 0. A
+        quota with value 0 means no value.
+        <span class="since">Only QEMU driver support since 0.10.0</span>
+      </dd>
+
     </dl>
 
 

docs/schemas/domaincommon.rng

@@ -581,6 +581,16 @@
               <ref name="cpuquota"/>
             </element>
           </optional>
+          <optional>
+            <element name="emulator_period">
+              <ref name="cpuperiod"/>
+            </element>
+          </optional>
+          <optional>
+            <element name="emulator_quota">
+              <ref name="cpuquota"/>
+            </element>
+          </optional>
           <zeroOrMore>
             <element name="vcpupin">
               <attribute name="vcpu">

src/conf/domain_conf.c

@@ -8344,6 +8344,14 @@ static virDomainDefPtr virDomainDefParseXML(virCapsPtr caps,
                          &def->cputune.quota) < 0)
         def->cputune.quota = 0;
 
+    if (virXPathULongLong("string(./cputune/emulator_period[1])", ctxt,
+                          &def->cputune.emulator_period) < 0)
+        def->cputune.emulator_period = 0;
+
+    if (virXPathLongLong("string(./cputune/emulator_quota[1])", ctxt,
+                         &def->cputune.emulator_quota) < 0)
+        def->cputune.emulator_quota = 0;
+
     if ((n = virXPathNodeSet("./cputune/vcpupin", ctxt, &nodes)) < 0) {
         goto error;
     }
@@ -13102,7 +13110,8 @@ virDomainDefFormatInternal(virDomainDefPtr def,
 
     if (def->cputune.shares || def->cputune.vcpupin ||
         def->cputune.period || def->cputune.quota ||
-        def->cputune.emulatorpin)
+        def->cputune.emulatorpin ||
+        def->cputune.emulator_period || def->cputune.emulator_quota)
         virBufferAddLit(buf, "  <cputune>\n");
 
     if (def->cputune.shares)
@@ -13114,6 +13123,17 @@ virDomainDefFormatInternal(virDomainDefPtr def,
     if (def->cputune.quota)
         virBufferAsprintf(buf, "    <quota>%lld</quota>\n",
                           def->cputune.quota);
+
+    if (def->cputune.emulator_period)
+        virBufferAsprintf(buf, "    <emulator_period>%llu"
+                          "</emulator_period>\n",
+                          def->cputune.emulator_period);
+
+    if (def->cputune.emulator_quota)
+        virBufferAsprintf(buf, "    <emulator_quota>%lld"
+                          "</emulator_quota>\n",
+                          def->cputune.emulator_quota);
+
     if (def->cputune.vcpupin) {
         for (i = 0; i < def->cputune.nvcpupin; i++) {
             virBufferAsprintf(buf, "    <vcpupin vcpu='%u' ",
@@ -13152,7 +13172,8 @@ virDomainDefFormatInternal(virDomainDefPtr def,
 
     if (def->cputune.shares || def->cputune.vcpupin ||
         def->cputune.period || def->cputune.quota ||
-        def->cputune.emulatorpin)
+        def->cputune.emulatorpin ||
+        def->cputune.emulator_period || def->cputune.emulator_quota)
         virBufferAddLit(buf, "  </cputune>\n");
 
     if (def->numatune.memory.nodemask ||

src/conf/domain_conf.h

@@ -1614,6 +1614,8 @@ struct _virDomainDef {
         unsigned long shares;
         unsigned long long period;
         long long quota;
+        unsigned long long emulator_period;
+        long long emulator_quota;
         int nvcpupin;
         virDomainVcpuPinDefPtr *vcpupin;
         virDomainVcpuPinDefPtr emulatorpin;

src/qemu/qemu_cgroup.c

@@ -564,7 +564,7 @@ int qemuSetupCgroupForVcpu(struct qemud_driver *driver, virDomainObjPtr vm)
     }
 
     if (priv->nvcpupids == 0 || priv->vcpupids[0] == vm->pid) {
-        /* If we does not know VCPU<->PID mapping or all vcpus run in the same
+        /* If we don't know VCPU<->PID mapping or all vcpu runs in the same
          * thread, we cannot control each vcpu.
          */
         virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
@@ -631,6 +631,8 @@ int qemuSetupCgroupForEmulator(struct qemud_driver *driver,
     virCgroupPtr cgroup = NULL;
     virCgroupPtr cgroup_emulator = NULL;
     virDomainDefPtr def = vm->def;
+    unsigned long long period = vm->def->cputune.emulator_period;
+    long long quota = vm->def->cputune.emulator_quota;
     int rc, i;
 
     if (driver->cgroup == NULL)
@@ -672,6 +674,13 @@ int qemuSetupCgroupForEmulator(struct qemud_driver *driver,
         qemuSetupCgroupEmulatorPin(cgroup_emulator, def->cputune.emulatorpin) < 0)
         goto cleanup;
 
+    if (period || quota) {
+        if (qemuCgroupControllerActive(driver, VIR_CGROUP_CONTROLLER_CPU)) {
+            if (qemuSetupCgroupVcpuBW(cgroup_emulator, period, quota) < 0)
+                goto cleanup;
+        }
+    }
+
     virCgroupFree(&cgroup_emulator);
     virCgroupFree(&cgroup);
     return 0;