diff mbox

[v2,2/3] Add event notification for guest balloon changes

Message ID 1337619593-25823-3-git-send-email-berrange@redhat.com
State New
Headers show

Commit Message

Daniel P. Berrangé May 21, 2012, 4:59 p.m. UTC 
From: "Daniel P. Berrange" <berrange@redhat.com>

After setting a balloon target value, applications have to
continually poll 'query-balloon' to determine whether the
guest has reacted to this request. The virtio-balloon backend
knows exactly when the guest has reacted though, and thus it
is possible to emit a JSON event to tell the mgmt application
whenever the guest balloon changes.

This introduces a new 'qemu_balloon_change()' API which is
to be called by balloon driver backends, whenever they have
a change in balloon value. This takes the 'actual' balloon
value, as would be found in the BalloonInfo struct.

The qemu_balloon_change API emits a JSON monitor event which
looks like:

  {"timestamp": {"seconds": 1337162462, "microseconds": 814521},
   "event": "BALLOON_CHANGE", "data": {"actual": 944766976}}

* balloon.c, balloon.h: Introduce qemu_balloon_change() for
  emitting balloon change events on the monitor
* hw/virtio-balloon.c: Invoke qemu_balloon_change() whenever
  the guest changes the balloon actual value
* monitor.c, monitor.h: Define QEVENT_BALLOON_CHANGE

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
---
 QMP/qmp-events.txt  |   18 ++++++++++++++++++
 balloon.c           |   14 ++++++++++++++
 balloon.h           |    2 ++
 hw/virtio-balloon.c |    5 +++++
 monitor.c           |    1 +
 monitor.h           |    1 +
 6 files changed, 41 insertions(+), 0 deletions(-)

Comments

Amit Shah May 22, 2012, 12:50 p.m. UTC | #1 
On (Mon) 21 May 2012 [20:50:55], Daniel P. Berrange wrote:
> On Tue, May 22, 2012 at 01:14:59AM +0530, Amit Shah wrote:
> > On (Mon) 21 May 2012 [17:59:52], Daniel P. Berrange wrote:
> > > From: "Daniel P. Berrange" <berrange@redhat.com>
> > > 
> > > After setting a balloon target value, applications have to
> > > continually poll 'query-balloon' to determine whether the
> > > guest has reacted to this request. The virtio-balloon backend
> > > knows exactly when the guest has reacted though, and thus it
> > > is possible to emit a JSON event to tell the mgmt application
> > > whenever the guest balloon changes.
> > > 
> > > This introduces a new 'qemu_balloon_change()' API which is
> > 
> > I prefer qemu_balloon_changed(), it is clearer that this is called
> > after a balloon value change.  qemu_balloon_change() can be taken to
> > mean the function is called as a response the the monitor 'balloon'
> > command.
> 
> Happy to change this.
> 
> > > +BALLOON_CHANGE
> > > +----------
> > 
> > similarly, this can be BALLOON_CHANGED
> 
> For the sake of consistency with the existing RTC_CHANGE event, I prefer
> the naming I already have.

OK, thinking about it, it seems alright for this to remain
BALLOON_CHANGE, as it's an event that originates from qemu for mgmt
apps, so there isn't ambiguity about it.

Maybe others can chime in?

		Amit
diff mbox

Patch

diff --git a/QMP/qmp-events.txt b/QMP/qmp-events.txt
index 9286af5..9ba7079 100644
--- a/QMP/qmp-events.txt
+++ b/QMP/qmp-events.txt
@@ -335,3 +335,21 @@  Example:
                "len": 10737418240, "offset": 134217728,
                "speed": 0 },
      "timestamp": { "seconds": 1267061043, "microseconds": 959568 } }
+
+
+BALLOON_CHANGE
+----------
+
+Emitted when the guest changes the actual BALLOON level. This
+value is equivalent to the 'actual' field return by the
+'query-balloon' command
+
+Data:
+
+- "actual": actual level of the guest memory balloon in bytes (json-number)
+
+Example:
+
+{ "event": "BALLOON_CHANGE",
+    "data": { "actual": 944766976 },
+    "timestamp": { "seconds": 1267020223, "microseconds": 435656 } }
diff --git a/balloon.c b/balloon.c
index aa354f7..913862b 100644
--- a/balloon.c
+++ b/balloon.c
@@ -30,6 +30,7 @@ 
 #include "balloon.h"
 #include "trace.h"
 #include "qmp-commands.h"
+#include "qjson.h"
 
 static QEMUBalloonEvent *balloon_event_fn;
 static QEMUBalloonStatus *balloon_stat_fn;
@@ -80,6 +81,19 @@  static int qemu_balloon_status(BalloonInfo *info)
     return 1;
 }
 
+void qemu_balloon_change(int64_t actual)
+{
+    QObject *data;
+
+    data = qobject_from_jsonf("{ 'actual': %" PRId64 " }",
+                              actual);
+
+    monitor_protocol_event(QEVENT_BALLOON_CHANGE, data);
+
+    qobject_decref(data);
+}
+
+
 BalloonInfo *qmp_query_balloon(Error **errp)
 {
     BalloonInfo *info;
diff --git a/balloon.h b/balloon.h
index b60fd5d..2ebac0d 100644
--- a/balloon.h
+++ b/balloon.h
@@ -24,4 +24,6 @@  int qemu_add_balloon_handler(QEMUBalloonEvent *event_func,
 			     QEMUBalloonStatus *stat_func, void *opaque);
 void qemu_remove_balloon_handler(void *opaque);
 
+void qemu_balloon_change(int64_t actual);
+
 #endif
diff --git a/hw/virtio-balloon.c b/hw/virtio-balloon.c
index ce9d2c9..9137573 100644
--- a/hw/virtio-balloon.c
+++ b/hw/virtio-balloon.c
@@ -146,8 +146,13 @@  static void virtio_balloon_set_config(VirtIODevice *vdev,
 {
     VirtIOBalloon *dev = to_virtio_balloon(vdev);
     struct virtio_balloon_config config;
+    uint32_t oldactual = dev->actual;
     memcpy(&config, config_data, 8);
     dev->actual = le32_to_cpu(config.actual);
+    if (dev->actual != oldactual) {
+        qemu_balloon_change(ram_size -
+                            (dev->actual << VIRTIO_BALLOON_PFN_SHIFT));
+    }
 }
 
 static uint32_t virtio_balloon_get_features(VirtIODevice *vdev, uint32_t f)
diff --git a/monitor.c b/monitor.c
index a3bc2c7..75fd4cf 100644
--- a/monitor.c
+++ b/monitor.c
@@ -443,6 +443,7 @@  static const char *monitor_event_names[] = {
     [QEVENT_DEVICE_TRAY_MOVED] = "DEVICE_TRAY_MOVED",
     [QEVENT_SUSPEND] = "SUSPEND",
     [QEVENT_WAKEUP] = "WAKEUP",
+    [QEVENT_BALLOON_CHANGE] = "BALLOON_CHANGE",
 };
 QEMU_BUILD_BUG_ON(ARRAY_SIZE(monitor_event_names) != QEVENT_MAX)
 
diff --git a/monitor.h b/monitor.h
index cd1d878..5f4de1b 100644
--- a/monitor.h
+++ b/monitor.h
@@ -41,6 +41,7 @@  typedef enum MonitorEvent {
     QEVENT_DEVICE_TRAY_MOVED,
     QEVENT_SUSPEND,
     QEVENT_WAKEUP,
+    QEVENT_BALLOON_CHANGE,
 
     /* Add to 'monitor_event_names' array in monitor.c when
      * defining new events here */