Allow balloon driver collection to be adjusted dynamically

Use the virDomainSetMemoryStatsPeriodFlags() to pass a period defined by
usage of a new --period option in order to set the collection period for the
balloon driver. This may enable or disable the collection based on the value.

Add the --current, --live, & --config options to dommemstat.

docs/formatdomain.html.in

@@ -4664,7 +4664,16 @@ qemu-kvm -net nic,model=? /dev/null
         <p>
           The optional <code>period</code> allows the QEMU virtio memory
           balloon driver to provide statistics through the <code>virsh
-          dommemstat [domain]</code> command.
+          dommemstat [domain]</code> command. By default, collection is
+          not enabled. In order to enable, use the <code>virsh dommemstat
+          [domain] --period [number]</code> command or <code>virsh edit</code>
+          command to add the option to the XML definition.
+          The <code>virsh dommemstat</code> will accept the options
+          <code>--live</code>, <code>--current</code>, or <code>--config</code>.
+          If an option is not provided, the change for a running domain will
+          only be made to the active guest.
+          If the QEMU driver is not at the right
+          revision, the attempt to set the period will fail.
           <span class='since'>Since 1.1.1, requires QEMU 1.5</span>
         </p>
       </dd>

tools/virsh-domain-monitor.c

@@ -314,6 +314,23 @@ static const vshCmdOptDef opts_dommemstat[] = {
      .flags = VSH_OFLAG_REQ,
      .help = N_("domain name, id or uuid")
     },
+    {.name = "period",
+     .type = VSH_OT_DATA,
+     .flags = VSH_OFLAG_REQ_OPT,
+     .help = N_("period in seconds to set collection")
+    },
+    {.name = "config",
+     .type = VSH_OT_BOOL,
+     .help = N_("affect next boot")
+    },
+    {.name = "live",
+     .type = VSH_OT_BOOL,
+     .help = N_("affect running domain")
+    },
+    {.name = "current",
+     .type = VSH_OT_BOOL,
+     .help = N_("affect current domain")
+    },
     {.name = NULL}
 };
 
@@ -325,15 +342,56 @@ cmdDomMemStat(vshControl *ctl, const vshCmd *cmd)
     struct _virDomainMemoryStat stats[VIR_DOMAIN_MEMORY_STAT_NR];
     unsigned int nr_stats;
     size_t i;
+    int ret = false;
+    int rv = 0;
+    int period = -1;
+    bool config = vshCommandOptBool(cmd, "config");
+    bool live = vshCommandOptBool(cmd, "live");
+    bool current = vshCommandOptBool(cmd, "current");
+    unsigned int flags = VIR_DOMAIN_AFFECT_CURRENT;
+
+    VSH_EXCLUSIVE_OPTIONS_VAR(current, live);
+    VSH_EXCLUSIVE_OPTIONS_VAR(current, config);
+    if (config)
+        flags |= VIR_DOMAIN_AFFECT_CONFIG;
+    if (live)
+        flags |= VIR_DOMAIN_AFFECT_LIVE;
 
     if (!(dom = vshCommandOptDomain(ctl, cmd, &name)))
         return false;
 
+    /* If none of the options were specified and we're active
+     * then be sure to allow active modification */
+    if (!current && !live && !config && virDomainIsActive(dom) == 1)
+        flags |= VIR_DOMAIN_AFFECT_LIVE;
+
+    /* Providing a period will adjust the balloon driver collection period.
+     * This is not really an unsigned long, but it
+     */
+    if ((rv = vshCommandOptInt(cmd, "period", &period)) < 0) {
+        vshError(ctl, "%s",
+                 _("Unable to parse integer parameter."));
+        goto cleanup;
+    }
+    if (rv > 0) {
+        if (period < 0) {
+            vshError(ctl, _("Invalid collection period value '%d'"), period);
+            goto cleanup;
+        }
+
+        if (virDomainSetMemoryStatsPeriod(dom, period, flags) < 0) {
+            vshError(ctl, "%s",
+                     _("Unable to change balloon collection period."));
+        } else {
+            ret = true;
+        }
+        goto cleanup;
+    }
+
     nr_stats = virDomainMemoryStats(dom, stats, VIR_DOMAIN_MEMORY_STAT_NR, 0);
     if (nr_stats == -1) {
         vshError(ctl, _("Failed to get memory statistics for domain %s"), name);
-        virDomainFree(dom);
-        return false;
+        goto cleanup;
     }
 
     for (i = 0; i < nr_stats; i++) {
@@ -355,8 +413,10 @@ cmdDomMemStat(vshControl *ctl, const vshCmd *cmd)
             vshPrint(ctl, "rss %llu\n", stats[i].val);
     }
 
+    ret = true;
+cleanup:
     virDomainFree(dom);
-    return true;
+    return ret;
 }
 
 /*

tools/virsh.pod

@@ -668,10 +668,30 @@ Both I<--live> and I<--current> flags may be given, but I<--current> is
 exclusive. If no flag is specified, behavior is different depending
 on hypervisor.
 
-=item B<dommemstat> I<domain>
+=item B<dommemstat> I<domain> [I<--period> B<seconds>]
+[[I<--config>] [I<--live>] | [I<--current>]]
 
 Get memory stats for a running domain.
 
+Depending on the hypervisor a variety of statistics can be returned
+
+For QEMU/KVM with a memory balloon, setting the optional I<--period> to a
+value larger than 0 in seconds will allow the balloon driver to return
+additional statistics which will be displayed by subsequent B<dommemstat>
+commands. Setting the I<--period> to 0 will stop the balloon driver collection,
+but does not clear the statistics in the balloon driver. Requires at least
+QEMU/KVM 1.5 to be running on the host.
+
+The I<--live>, I<--config>, and I<--current> flags are only valid when using
+the I<--period> option in order to set the collection period for the balloon
+driver. If I<--live> is specified, only the running guest collection period
+is affected. If I<--config> is specified, affect the next boot of a persistent
+guest. If I<--current> is specified, affect the current guest state.
+
+Both I<--live> and I<--config> flags may be given, but I<--current> is
+exclusive. If no flag is specified, behavior is different depending
+on the guest state.
+
 =item B<domblkerror> I<domain>
 
 Show errors on block devices.  This command usually comes handy when