virtio: Add memory statistics reporting to the balloon driver

When using ballooning to manage overcommitted memory on a host, a system for
guests to communicate their memory usage to the host can provide information
that will minimize the impact of ballooning on the guests.  The current method
employs a daemon running in each guest that communicates memory statistics to a
host daemon at a specified time interval.  The host daemon aggregates this
information and inflates and/or deflates balloons according to the level of
host memory pressure.  This approach is effective but overly complex since a
daemon must be installed inside each guest and coordinated to communicate with
the host.  A simpler approach is to collect memory statistics in the virtio
balloon driver and communicate them directly to the hypervisor.

Signed-off-by: Adam Litke <agl@us.ibm.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/balloon.h b/balloon.h
index 60b4a5de7b..c3a1ad365d 100644
--- a/balloon.h
+++ b/balloon.h
@@ -16,12 +16,13 @@
 
 #include "cpu-defs.h"
 
-typedef ram_addr_t (QEMUBalloonEvent)(void *opaque, ram_addr_t target);
+typedef void (QEMUBalloonEvent)(void *opaque, ram_addr_t target,
+                                MonitorCompletion cb, void *cb_data);
 
 void qemu_add_balloon_handler(QEMUBalloonEvent *func, void *opaque);
 
-void qemu_balloon(ram_addr_t target);
+int qemu_balloon(ram_addr_t target, MonitorCompletion cb, void *opaque);
 
-ram_addr_t qemu_balloon_status(void);
+int qemu_balloon_status(MonitorCompletion cb, void *opaque);
 
 #endif