qemu_cgroup: Introduce cgroup functions for IOThreads

In order to support cpuset setting, introduce qemuSetupCgroupIOThreadsPin
and qemuSetupCgroupForIOThreads to mimic the existing Vcpu API's.

These will support having an 'iotrhreadpin' element in the 'cpuset' in
order to pin named IOThreads to specific CPU's. The IOThread pin names
will follow the IOThread naming scheme starting at 1 (eg "iothread1")
up through an including the def->iothreads value.

src/qemu/qemu_cgroup.c

@@ -902,6 +902,23 @@ qemuSetupCgroupVcpuPin(virCgroupPtr cgroup,
     return -1;
 }
 
+int
+qemuSetupCgroupIOThreadsPin(virCgroupPtr cgroup,
+                            virDomainVcpuPinDefPtr *iothreadspin,
+                            int niothreadspin,
+                            int iothreadid)
+{
+    size_t i;
+
+    for (i = 0; i < niothreadspin; i++) {
+        if (iothreadid == iothreadspin[i]->vcpuid) {
+            return qemuSetupCgroupEmulatorPin(cgroup, iothreadspin[i]->cpumask);
+        }
+    }
+
+    return -1;
+}
+
 int
 qemuSetupCgroupEmulatorPin(virCgroupPtr cgroup,
                            virBitmapPtr cpumask)
@@ -1082,6 +1099,93 @@ qemuSetupCgroupForEmulator(virQEMUDriverPtr driver,
     return -1;
 }
 
+int
+qemuSetupCgroupForIOThreads(virDomainObjPtr vm)
+{
+    virCgroupPtr cgroup_iothread = NULL;
+    qemuDomainObjPrivatePtr priv = vm->privateData;
+    virDomainDefPtr def = vm->def;
+    size_t i, j;
+    unsigned long long period = vm->def->cputune.period;
+    long long quota = vm->def->cputune.quota;
+
+    if ((period || quota) &&
+        !virCgroupHasController(priv->cgroup, VIR_CGROUP_CONTROLLER_CPU)) {
+        virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                       _("cgroup cpu is required for scheduler tuning"));
+        return -1;
+    }
+
+    /*
+     * If CPU cgroup controller is not initialized here, then we need
+     * neither period nor quota settings.  And if CPUSET controller is
+     * not initialized either, then there's nothing to do anyway.
+     */
+    if (!virCgroupHasController(priv->cgroup, VIR_CGROUP_CONTROLLER_CPU) &&
+        !virCgroupHasController(priv->cgroup, VIR_CGROUP_CONTROLLER_CPUSET))
+        return 0;
+
+    /* We are trying to setup cgroups for CPU pinning, which can also be done
+     * with virProcessSetAffinity, thus the lack of cgroups is not fatal here.
+     */
+    if (priv->cgroup == NULL)
+        return 0;
+
+    if (priv->niothreadpids == 0) {
+        VIR_WARN("Unable to get iothreads' pids.");
+        return 0;
+    }
+
+    for (i = 0; i < priv->niothreadpids; i++) {
+        /* IOThreads are numbered 1..n, although the array is 0..n-1,
+         * so we will account for that here
+         */
+        if (virCgroupNewIOThread(priv->cgroup, i+1, true, &cgroup_iothread) < 0)
+            goto cleanup;
+
+        /* move the thread for iothread to sub dir */
+        if (virCgroupAddTask(cgroup_iothread, priv->iothreadpids[i]) < 0)
+            goto cleanup;
+
+        if (period || quota) {
+            if (qemuSetupCgroupVcpuBW(cgroup_iothread, period, quota) < 0)
+                goto cleanup;
+        }
+
+        /* Set iothreadpin in cgroup if iothreadpin xml is provided */
+        if (virCgroupHasController(priv->cgroup,
+                                   VIR_CGROUP_CONTROLLER_CPUSET)) {
+            /* find the right CPU to pin, otherwise
+             * qemuSetupCgroupIOThreadsPin will fail. */
+            for (j = 0; j < def->cputune.niothreadspin; j++) {
+                /* IOThreads are numbered/named 1..n */
+                if (def->cputune.iothreadspin[j]->vcpuid != i+1)
+                    continue;
+
+                if (qemuSetupCgroupIOThreadsPin(cgroup_iothread,
+                                                def->cputune.iothreadspin,
+                                                def->cputune.niothreadspin,
+                                                i+1) < 0)
+                    goto cleanup;
+
+                break;
+            }
+        }
+
+        virCgroupFree(&cgroup_iothread);
+    }
+
+    return 0;
+
+ cleanup:
+    if (cgroup_iothread) {
+        virCgroupRemove(cgroup_iothread);
+        virCgroupFree(&cgroup_iothread);
+    }
+
+    return -1;
+}
+
 int
 qemuRemoveCgroup(virDomainObjPtr vm)
 {

src/qemu/qemu_cgroup.h

@@ -57,7 +57,12 @@ int qemuSetupCgroupVcpuPin(virCgroupPtr cgroup,
                            int nvcpupin,
                            int vcpuid);
 int qemuSetupCgroupEmulatorPin(virCgroupPtr cgroup, virBitmapPtr cpumask);
+int qemuSetupCgroupIOThreadsPin(virCgroupPtr cgroup,
+                                virDomainVcpuPinDefPtr *iothreadspin,
+                                int niothreadspin,
+                                int iothreadid);
 int qemuSetupCgroupForVcpu(virDomainObjPtr vm);
+int qemuSetupCgroupForIOThreads(virDomainObjPtr vm);
 int qemuSetupCgroupForEmulator(virQEMUDriverPtr driver,
                                virDomainObjPtr vm,
                                virBitmapPtr nodemask);