-virtio balloon memory statistics
+Virtio balloon memory statistics
================================
The virtio balloon driver supports guest memory statistics reporting. These
This is done by writing a time interval value (in seconds) to the
guest-stats-polling-interval property. This value can be:
- > 0 enables polling in the specified interval. If polling is already
+ > 0
+ enables polling in the specified interval. If polling is already
enabled, the polling time interval is changed to the new value
- 0 disables polling. Previous polled statistics are still valid and
+ 0
+ disables polling. Previous polled statistics are still valid and
can be queried.
Once polling is enabled, the virtio-balloon device in QEMU will start
To retrieve those stats, clients have to query the guest-stats property,
which will return a dictionary containing:
- o A key named 'stats', containing all available stats. If the guest
+ * A key named 'stats', containing all available stats. If the guest
doesn't support a particular stat, or if it couldn't be retrieved,
its value will be -1. Currently, the following stats are supported:
- stat-htlb-pgalloc
- stat-htlb-pgfail
- o A key named last-update, which contains the last stats update
+ * A key named last-update, which contains the last stats update
timestamp in seconds. Since this timestamp is generated by the host,
a buggy guest can't influence its value. The value is 0 if the guest
has not updated the stats (yet).
respond to the request the timer will never be re-armed, which has
the same effect as disabling polling
-Here are a few examples. QEMU is started with '-device virtio-balloon',
-which generates '/machine/peripheral-anon/device[1]' as the QOM path for
+Here are a few examples. QEMU is started with ``-device virtio-balloon``,
+which generates ``/machine/peripheral-anon/device[1]`` as the QOM path for
the balloon device.
-Enable polling with 2 seconds interval:
+Enable polling with 2 seconds interval::
-{ "execute": "qom-set",
- "arguments": { "path": "/machine/peripheral-anon/device[1]",
- "property": "guest-stats-polling-interval", "value": 2 } }
+ { "execute": "qom-set",
+ "arguments": { "path": "/machine/peripheral-anon/device[1]",
+ "property": "guest-stats-polling-interval", "value": 2 } }
-{ "return": {} }
+ { "return": {} }
-Change polling to 10 seconds:
+Change polling to 10 seconds::
-{ "execute": "qom-set",
- "arguments": { "path": "/machine/peripheral-anon/device[1]",
- "property": "guest-stats-polling-interval", "value": 10 } }
+ { "execute": "qom-set",
+ "arguments": { "path": "/machine/peripheral-anon/device[1]",
+ "property": "guest-stats-polling-interval", "value": 10 } }
-{ "return": {} }
+ { "return": {} }
-Get stats:
+Get stats::
-{ "execute": "qom-get",
- "arguments": { "path": "/machine/peripheral-anon/device[1]",
- "property": "guest-stats" } }
-{
+ { "execute": "qom-get",
+ "arguments": { "path": "/machine/peripheral-anon/device[1]",
+ "property": "guest-stats" } }
+ {
"return": {
"stats": {
"stat-swap-out": 0,
},
"last-update": 1358529861
}
-}
+ }
-Disable polling:
+Disable polling::
-{ "execute": "qom-set",
- "arguments": { "path": "/machine/peripheral-anon/device[1]",
- "property": "stats-polling-interval", "value": 0 } }
+ { "execute": "qom-set",
+ "arguments": { "path": "/machine/peripheral-anon/device[1]",
+ "property": "stats-polling-interval", "value": 0 } }
-{ "return": {} }
+ { "return": {} }