[PATCH 3/3] migration/colo: Merge multi checkpoint request into one.

[Zhang Chen <chen.zhang@intel.com >]

From: Zhang Chen <chen.zhang@intel.com>

When COLO guest occur issues, COLO-compare will catch lots of
different network packet and trigger notification multi times,
force periodic may happen at the same time. So this can be
efficient merge checkpoint request within COLO_CHECKPOINT_INTERVAL.

Signed-off-by: Zhang Chen <chen.zhang@intel.com>
---
 migration/colo.c | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/migration/colo.c b/migration/colo.c
index d5bced22cb..e6a7d8c6e2 100644
--- a/migration/colo.c
+++ b/migration/colo.c
@@ -47,6 +47,9 @@ static COLOMode last_colo_mode;
 
 #define COLO_BUFFER_BASE_SIZE (4 * 1024 * 1024)
 
+/* Default COLO_CHECKPOINT_INTERVAL is 1000 ms */
+#define COLO_CHECKPOINT_INTERVAL 1000
+
 bool migration_in_colo_state(void)
 {
     MigrationState *s = migrate_get_current();
@@ -651,13 +654,20 @@ out:
 void colo_checkpoint_notify(void *opaque)
 {
     MigrationState *s = opaque;
-    int64_t next_notify_time;
+    int64_t now = qemu_clock_get_ms(QEMU_CLOCK_HOST);
 
-    qemu_sem_post(&s->colo_checkpoint_sem);
-    s->colo_checkpoint_time = qemu_clock_get_ms(QEMU_CLOCK_HOST);
-    next_notify_time = s->colo_checkpoint_time +
-                    s->parameters.x_checkpoint_delay;
-    timer_mod(s->colo_delay_timer, next_notify_time);
+    /*
+     * When COLO guest occur issues, COLO-compare will catch lots of
+     * different network packet and trigger notification multi times,
+     * force periodic may happen at the same time. So this can be
+     * efficient merge checkpoint request within COLO_CHECKPOINT_INTERVAL.
+     */
+    if (now > s->colo_checkpoint_time + COLO_CHECKPOINT_INTERVAL) {
+        qemu_sem_post(&s->colo_checkpoint_sem);
+        timer_mod(s->colo_delay_timer, now +
+                  s->parameters.x_checkpoint_delay);
+        s->colo_checkpoint_time = now;
+    }
 }
 
 void migrate_start_colo_process(MigrationState *s)
-- 
2.17.1