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[libvirt] [PATCHv6 4/5] blkiotune: add interface for blkiotune.device_weight



This adds per-device weights to <blkiotune>.  Note that the
cgroups implementation only supports weights per block device,
and not per-file within the device; hence this option must be
global to the domain definition rather than tied to individual
<device>/<disk> entries:

<domain ...>
  <blkiotune>
    <device>
      <path>/path/to/block</path>
      <weight>1000</weight>
    </device>
  </blkiotune>
...

This patch also adds a parameter --device-weight to virsh command
blkiotune for setting/getting blkiotune.weight_device for any
hypervisor that supports it.  All <device> entries under
<blkiotune> are concatenated into a single string attribute under
virDomain{Get,Set}BlkioParameters, named "device_weight".
---

v5: did not include this patch
v6: split v4 2/2 into two parts; this part covers just the libvirt.h
and virsh changes.  Rename public-facing terminology to be
"device_weight", not "weight_device", since we are talking about
per-device weights and may later add other per-device attributes
(no need to propagate cgroups' stupid naming to the user).  Rebase
to fit in with VIR_TYPED_PARAM_STRING tweaks earlier in series.

Should we use just commas for field separation, rather than commas
between device and weight but semicolon between device-weight pairs?
It would make it much easier to do:
virsh blkiotune dom --device-weight /dev/sda,500,/dev/sdb,500
instead of requiring shell quoting:
virsh blkiotune dom --device-weight '/dev/sda,500;/dev/sdb,500'

 docs/formatdomain.html.in     |   29 ++++++++-
 docs/schemas/domaincommon.rng |   12 ++++
 include/libvirt/libvirt.h.in  |   10 +++
 src/conf/domain_conf.c        |  130 ++++++++++++++++++++++++++++++++++++++++-
 src/conf/domain_conf.h        |   17 +++++
 src/libvirt_private.syms      |    2 +
 tools/virsh.c                 |   32 +++++++++-
 tools/virsh.pod               |    6 ++-
 8 files changed, 228 insertions(+), 10 deletions(-)

diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
index cbad196..e848b7d 100644
--- a/docs/formatdomain.html.in
+++ b/docs/formatdomain.html.in
@@ -505,6 +505,14 @@
   ...
   &lt;blkiotune&gt;
     &lt;weight&gt;800&lt;/weight&gt;
+    &lt;device&gt;
+      &lt;path&gt;/dev/sda&lt;/path&gt;
+      &lt;weight&gt;1000&lt;/weight&gt;
+    &lt;/device&gt;
+    &lt;device&gt;
+      &lt;path&gt;/dev/sdb&lt;/path&gt;
+      &lt;weight&gt;500&lt;/weight&gt;
+    &lt;/device&gt;
   &lt;/blkiotune&gt;
   ...
 &lt;/domain&gt;
@@ -514,10 +522,25 @@
       <dt><code>blkiotune</code></dt>
       <dd> The optional <code>blkiotune</code> element provides the ability
         to tune Blkio cgroup tunable parameters for the domain. If this is
-        omitted, it defaults to the OS provided defaults.</dd>
+        omitted, it defaults to the OS provided
+        defaults. <span class="since">Since 0.8.8</span></dd>
       <dt><code>weight</code></dt>
-      <dd> The optional <code>weight</code> element is the I/O weight of the
-        guest. The value should be in range [100, 1000].</dd>
+      <dd> The optional <code>weight</code> element is the overall I/O
+        weight of the guest. The value should be in the range [100,
+        1000].</dd>
+      <dt><code>device</code></dt>
+      <dd>The domain may have multiple <code>device</code> elements
+        that further tune the weights for each host block device in
+        use by the domain.  Note that
+        multiple <a href="#elementsDisks">guest disks</a> can share a
+        single host block device, if they are backed by files within
+        the same host file system, which is why this tuning parameter
+        is at the global domain level rather than associated with each
+        guest disk device.  Each <code>device</code> element has two
+        mandatory sub-elements, <code>path</code> describing the
+        absolute path of the device, and <code>weight</code> giving
+        the relative weight of that device, in the range [100,
+        1000].  <span class="since">Since 0.9.7</span></dd>
     </dl>


diff --git a/docs/schemas/domaincommon.rng b/docs/schemas/domaincommon.rng
index b6f858e..6f96fe2 100644
--- a/docs/schemas/domaincommon.rng
+++ b/docs/schemas/domaincommon.rng
@@ -328,6 +328,18 @@
               <ref name="weight"/>
             </element>
           </optional>
+          <zeroOrMore>
+            <element name="device">
+              <interleave>
+                <element name="path">
+                  <ref name="absFilePath"/>
+                </element>
+                <element name="weight">
+                  <data type="int"/>
+                </element>
+              </interleave>
+            </element>
+          </zeroOrMore>
         </element>
       </optional>

diff --git a/include/libvirt/libvirt.h.in b/include/libvirt/libvirt.h.in
index e10a72b..5ae7d10 100644
--- a/include/libvirt/libvirt.h.in
+++ b/include/libvirt/libvirt.h.in
@@ -1236,6 +1236,16 @@ char *                  virDomainGetSchedulerType(virDomainPtr domain,

 #define VIR_DOMAIN_BLKIO_WEIGHT "weight"

+/**
+ * VIR_DOMAIN_BLKIO_DEVICE_WEIGHT:
+ *
+ * Macro for the blkio tunable weight_device: it represents the
+ * per-device weight, as a string.  The string is parsed as a
+ * series of /path/to/device,weight elements, separated by ';'.
+ */
+
+#define VIR_DOMAIN_BLKIO_DEVICE_WEIGHT "device_weight"
+
 /* Set Blkio tunables for the domain*/
 int     virDomainSetBlkioParameters(virDomainPtr domain,
                                     virTypedParameterPtr params,
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 238edfd..e5b5f69 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -603,6 +603,99 @@ VIR_ENUM_IMPL(virDomainStartupPolicy, VIR_DOMAIN_STARTUP_POLICY_LAST,
 #define VIR_DOMAIN_XML_WRITE_FLAGS  VIR_DOMAIN_XML_SECURE
 #define VIR_DOMAIN_XML_READ_FLAGS   VIR_DOMAIN_XML_INACTIVE

+
+void virBlkioDeviceWeightArrayClear(virBlkioDeviceWeightPtr deviceWeights,
+                                    int ndevices)
+{
+    int i;
+
+    for (i = 0; i < ndevices; i++)
+        VIR_FREE(deviceWeights[i].path);
+}
+
+/**
+ * virBlkioDeviceWeightToStr:
+ *
+ * This function returns a string representing device weights that is
+ * suitable for writing to /cgroup/blkio/blkio.weight_device, given
+ * a list of per-device weights.
+ */
+#if defined(major) && defined(minor)
+int virBlkioDeviceWeightToStr(virBlkioDeviceWeightPtr devices,
+                              int ndevices,
+                              char **result)
+{
+    int i;
+    struct stat s;
+    virBuffer buf = VIR_BUFFER_INITIALIZER;
+
+    for (i = 0; i < ndevices; i++) {
+        if (stat(devices[i].path, &s) == -1)
+            return -1;
+        if ((s.st_mode & S_IFMT) != S_IFBLK)
+            return -1;
+        virBufferAsprintf(&buf, "%d:%d %d\n",
+                          major(s.st_rdev),
+                          minor(s.st_rdev),
+                          devices[i].weight);
+    }
+
+    if (virBufferError(&buf))
+        return -1;
+
+    *result = virBufferContentAndReset(&buf);
+    return 0;
+}
+#else
+int virBlkioDeviceWeightToStr(virBlkioDeviceWeightPtr devices ATTRIBUTE_UNUSED,
+                              int ndevices ATTRIBUTE_UNUSED,
+                              char **result ATTRIBUTE_UNUSED)
+{
+    return -1;
+}
+#endif
+
+/**
+ * virDomainBlkioDeviceWeightParseXML
+ *
+ * this function parses a XML node:
+ *
+ *   <device>
+ *     <path>/fully/qualified/device/path</path>
+ *     <weight>weight</weight>
+ *   </device>
+ *
+ * and fills a virBlkioDeviceWeight struct.
+ */
+static int virDomainBlkioDeviceWeightParseXML(xmlNodePtr root,
+                                              virBlkioDeviceWeightPtr dw)
+{
+    char *c;
+    xmlNodePtr node;
+
+    if (!dw)
+        return -1;
+
+    node = root->children;
+    while (node) {
+        if (node->type == XML_ELEMENT_NODE) {
+            if (xmlStrEqual(node->name, BAD_CAST "path")) {
+                dw->path = (char *)xmlNodeGetContent(node);
+            } else if (xmlStrEqual(node->name, BAD_CAST "weight")) {
+                c = (char *)xmlNodeGetContent(node);
+                if (virStrToLong_i(c, NULL, 10, &dw->weight) < 0)
+                    return -1;
+                VIR_FREE(c);
+            }
+        }
+        node = node->next;
+    }
+
+    return 0;
+}
+
+
+
 static void
 virDomainObjListDataFree(void *payload, const void *name ATTRIBUTE_UNUSED)
 {
@@ -1272,6 +1365,10 @@ void virDomainDefFree(virDomainDefPtr def)
     VIR_FREE(def->emulator);
     VIR_FREE(def->description);

+    virBlkioDeviceWeightArrayClear(def->blkio.devices,
+                                   def->blkio.ndevices);
+    VIR_FREE(def->blkio.devices);
+
     virDomainWatchdogDefFree(def->watchdog);

     virDomainMemballoonDefFree(def->memballoon);
@@ -6710,6 +6807,21 @@ static virDomainDefPtr virDomainDefParseXML(virCapsPtr caps,
                      &def->blkio.weight) < 0)
         def->blkio.weight = 0;

+    n = virXPathNodeSet("./blkiotune/device", ctxt, &nodes);
+    if (n > 0) {
+        if (VIR_ALLOC_N(def->blkio.devices, n) < 0) {
+            virReportOOMError();
+            goto error;
+        }
+
+        for (i = 0; i < n; i++) {
+            virDomainBlkioDeviceWeightParseXML(nodes[i],
+                                               &def->blkio.devices[i]);
+        }
+        def->blkio.ndevices = n;
+        VIR_FREE(nodes);
+    }
+
     /* Extract other memory tunables */
     if (virXPathULong("string(./memtune/hard_limit)", ctxt,
                       &def->mem.hard_limit) < 0)
@@ -10848,10 +10960,22 @@ virDomainDefFormatInternal(virDomainDefPtr def,
                       def->mem.cur_balloon);

     /* add blkiotune only if there are any */
-    if (def->blkio.weight) {
+    if (def->blkio.weight || def->blkio.devices) {
         virBufferAddLit(buf, "  <blkiotune>\n");
-        virBufferAsprintf(buf, "    <weight>%u</weight>\n",
-                          def->blkio.weight);
+
+        if (def->blkio.weight)
+            virBufferAsprintf(buf, "    <weight>%u</weight>\n",
+                              def->blkio.weight);
+
+        for (n = 0; n < def->blkio.ndevices; n++) {
+            virBufferAddLit(buf, "    <device>\n");
+            virBufferEscapeString(buf, "      <path>%s</path>\n",
+                                  def->blkio.devices[n].path);
+            virBufferAsprintf(buf, "      <weight>%d</weight>\n",
+                              def->blkio.devices[n].weight);
+            virBufferAddLit(buf, "    </device>\n");
+        }
+
         virBufferAddLit(buf, "  </blkiotune>\n");
     }

diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index 5ebb441..577d10d 100644
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -1361,6 +1361,20 @@ struct _virDomainNumatuneDef {
     /* Future NUMA tuning related stuff should go here. */
 };

+typedef struct _virBlkioDeviceWeight virBlkioDeviceWeight;
+typedef virBlkioDeviceWeight *virBlkioDeviceWeightPtr;
+struct _virBlkioDeviceWeight {
+    char *path;
+    int weight;
+};
+
+void virBlkioDeviceWeightArrayClear(virBlkioDeviceWeightPtr deviceWeights,
+                                    int ndevices);
+int virBlkioDeviceWeightToStr(virBlkioDeviceWeightPtr deviceWeights,
+                              int ndevices,
+                              char **result);
+
+
 /*
  * Guest VM main configuration
  *
@@ -1378,6 +1392,9 @@ struct _virDomainDef {

     struct {
         unsigned int weight;
+
+        size_t ndevices;
+        virBlkioDeviceWeightPtr devices;
     } blkio;

     struct {
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 2185294..f7d0fb2 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -231,6 +231,8 @@ virDomainAuditVcpu;


 # domain_conf.h
+virBlkioDeviceWeightArrayClear;
+virBlkioDeviceWeightToStr;
 virDiskNameToBusDeviceIndex;
 virDiskNameToIndex;
 virDomainActualNetDefFree;
diff --git a/tools/virsh.c b/tools/virsh.c
index 5544a41..ca8db70 100644
--- a/tools/virsh.c
+++ b/tools/virsh.c
@@ -4648,6 +4648,8 @@ static const vshCmdOptDef opts_blkiotune[] = {
     {"domain", VSH_OT_DATA, VSH_OFLAG_REQ, N_("domain name, id or uuid")},
     {"weight", VSH_OT_INT, VSH_OFLAG_NONE,
      N_("IO Weight in range [100, 1000]")},
+    {"device-weight", VSH_OT_STRING, VSH_OFLAG_NONE,
+     N_("per-device IO Weights, in the form of /path/to/device,weight;...")},
     {"config", VSH_OT_BOOL, 0, N_("affect next boot")},
     {"live", VSH_OT_BOOL, 0, N_("affect running domain")},
     {"current", VSH_OT_BOOL, 0, N_("affect current domain")},
@@ -4658,6 +4660,7 @@ static bool
 cmdBlkiotune(vshControl * ctl, const vshCmd * cmd)
 {
     virDomainPtr dom;
+    const char *device_weight = NULL;
     int weight = 0;
     int nparams = 0;
     int rv = 0;
@@ -4702,6 +4705,16 @@ cmdBlkiotune(vshControl * ctl, const vshCmd * cmd)
         }
     }

+    rv = vshCommandOptString(cmd, "device-weight", &device_weight);
+    if (rv < 0) {
+        vshError(ctl, "%s",
+                 _("Unable to parse string parameter"));
+        goto cleanup;
+    }
+    if (rv > 0) {
+        nparams++;
+    }
+
     if (nparams == 0) {
         /* get the number of blkio parameters */
         if (virDomainGetBlkioParameters(dom, NULL, &nparams, flags) != 0) {
@@ -4749,6 +4762,10 @@ cmdBlkiotune(vshControl * ctl, const vshCmd * cmd)
                     vshPrint(ctl, "%-15s: %d\n", params[i].field,
                              params[i].value.b);
                     break;
+                case VIR_TYPED_PARAM_STRING:
+                    vshPrint(ctl, "%-15s: %s\n", params[i].field,
+                             params[i].value.s);
+                    break;
                 default:
                     vshPrint(ctl, "unimplemented blkio parameter type\n");
             }
@@ -4769,11 +4786,20 @@ cmdBlkiotune(vshControl * ctl, const vshCmd * cmd)
                         sizeof(temp->field));
                 weight = 0;
             }
+
+            if (device_weight) {
+                /* Safe to cast away const here.  */
+                temp->value.s = (char *)device_weight;
+                temp->type = VIR_TYPED_PARAM_STRING;
+                strncpy(temp->field, VIR_DOMAIN_BLKIO_DEVICE_WEIGHT,
+                        sizeof(temp->field));
+            }
         }
-        if (virDomainSetBlkioParameters(dom, params, nparams, flags) != 0)
+        ret = true;
+        if (virDomainSetBlkioParameters(dom, params, nparams, flags) != 0) {
             vshError(ctl, "%s", _("Unable to change blkio parameters"));
-        else
-            ret = true;
+            ret = false;
+        }
     }

   cleanup:
diff --git a/tools/virsh.pod b/tools/virsh.pod
index 775d302..a117e84 100644
--- a/tools/virsh.pod
+++ b/tools/virsh.pod
@@ -1032,12 +1032,16 @@ value are kilobytes (i.e. blocks of 1024 bytes).

 Specifying -1 as a value for these limits is interpreted as unlimited.

-=item B<blkiotune> I<domain-id> [I<--weight> B<weight>] [[I<--config>]
+=item B<blkiotune> I<domain-id> [I<--weight> B<weight>]
+[I<--device-weight> B<device-weights>] [[I<--config>]
 [I<--live>] | [I<--current>]]

 Display or set the blkio parameters. QEMU/KVM supports I<--weight>.
 I<--weight> is in range [100, 1000].

+B<device-weights> is a single string listing one or more device/weight
+pairs, in the format of /path/to/device,weight;/path/to/device,weight.
+
 If I<--live> is specified, affect a running guest.
 If I<--config> is specified, affect the next boot of a persistent guest.
 If I<--current> is specified, affect the current guest state.
-- 
1.7.4.4


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