[Qemu-devel] [PATCH v2 4/6] Migration: Emit event at start of pass

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Emit an event each time we sync the dirty bitmap on the source;
this helps libvirt use postcopy by giving it a kick when it
might be a good idea to start the postcopy.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 docs/qmp-events.txt | 14 ++++++++++++++
 migration/ram.c     |  4 ++++
 qapi/event.json     | 13 +++++++++++++
 3 files changed, 31 insertions(+)

diff --git a/docs/qmp-events.txt b/docs/qmp-events.txt
index d2f1ce4..52eb7e2 100644
--- a/docs/qmp-events.txt
+++ b/docs/qmp-events.txt
@@ -496,6 +496,20 @@ Example:
 {"timestamp": {"seconds": 1432121972, "microseconds": 744001},
  "event": "MIGRATION", "data": {"status": "completed"}}
 
+MIGRATION_PASS
+--------------
+
+Emitted from the source side of a migration at the start of each pass
+(when it syncs the dirty bitmap)
+
+Data: None.
+
+  - "pass": An incrementing count (starting at 1 on the first pass)
+
+Example:
+{"timestamp": {"seconds": 1449669631, "microseconds": 239225},
+ "event": "MIGRATION_PASS", "data": {"pass": 2}}
+
 STOP
 ----
 
diff --git a/migration/ram.c b/migration/ram.c
index 0490f00..102d1f2 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -27,6 +27,7 @@
  */
 #include <stdint.h>
 #include <zlib.h>
+#include "qapi-event.h"
 #include "qemu/bitops.h"
 #include "qemu/bitmap.h"
 #include "qemu/timer.h"
@@ -682,6 +683,9 @@ static void migration_bitmap_sync(void)
         num_dirty_pages_period = 0;
     }
     s->dirty_sync_count = bitmap_sync_count;
+    if (migrate_use_events()) {
+        qapi_event_send_migration_pass(bitmap_sync_count, NULL);
+    }
 }
 
 /**
diff --git a/qapi/event.json b/qapi/event.json
index f0cef01..390fd45 100644
--- a/qapi/event.json
+++ b/qapi/event.json
@@ -255,6 +255,19 @@
   'data': {'status': 'MigrationStatus'}}
 
 ##
+# @MIGRATION_PASS
+#
+# Emitted from the source side of a migration at the start of each pass
+# (when it syncs the dirty bitmap)
+#
+# @pass: An incrementing count (starting at 1 on the first pass)
+#
+# Since: 2.6
+##
+{ 'event': 'MIGRATION_PASS',
+  'data': { 'pass': 'int' } }
+
+##
 # @ACPI_DEVICE_OST
 #
 # Emitted when guest executes ACPI _OST method.
-- 
2.5.0