[PATCH v1 3/7] qapi/migration: Introduce the iteration-count

[Hyman Huang <yong.huang@smartx.com>]

The original migration information dirty-sync-count could
no longer reflect iteration count due to the introduction
of background synchronization in the next commit;
add the iteration count to compensate.

Signed-off-by: Hyman Huang <yong.huang@smartx.com>
---
 migration/migration-stats.h  |  4 ++++
 migration/migration.c        |  1 +
 migration/ram.c              | 12 ++++++++----
 qapi/migration.json          |  6 +++++-
 tests/qtest/migration-test.c |  2 +-
 5 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/migration/migration-stats.h b/migration/migration-stats.h
index 05290ade76..43ee0f4f05 100644
--- a/migration/migration-stats.h
+++ b/migration/migration-stats.h
@@ -50,6 +50,10 @@ typedef struct {
      * Number of times we have synchronized guest bitmaps.
      */
     Stat64 dirty_sync_count;
+    /*
+     * Number of migration iteration processed.
+     */
+    Stat64 iteration_count;
     /*
      * Number of times zero copy failed to send any page using zero
      * copy.
diff --git a/migration/migration.c b/migration/migration.c
index 3dea06d577..055d527ff6 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -1197,6 +1197,7 @@ static void populate_ram_info(MigrationInfo *info, MigrationState *s)
     info->ram->mbps = s->mbps;
     info->ram->dirty_sync_count =
         stat64_get(&mig_stats.dirty_sync_count);
+    info->ram->iteration_count = stat64_get(&mig_stats.iteration_count);
     info->ram->dirty_sync_missed_zero_copy =
         stat64_get(&mig_stats.dirty_sync_missed_zero_copy);
     info->ram->postcopy_requests =
diff --git a/migration/ram.c b/migration/ram.c
index e205806a5f..ca5a1b5f16 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -594,7 +594,7 @@ static void xbzrle_cache_zero_page(ram_addr_t current_addr)
     /* We don't care if this fails to allocate a new cache page
      * as long as it updated an old one */
     cache_insert(XBZRLE.cache, current_addr, XBZRLE.zero_target_page,
-                 stat64_get(&mig_stats.dirty_sync_count));
+                 stat64_get(&mig_stats.iteration_count));
 }
 
 #define ENCODING_FLAG_XBZRLE 0x1
@@ -620,7 +620,7 @@ static int save_xbzrle_page(RAMState *rs, PageSearchStatus *pss,
     int encoded_len = 0, bytes_xbzrle;
     uint8_t *prev_cached_page;
     QEMUFile *file = pss->pss_channel;
-    uint64_t generation = stat64_get(&mig_stats.dirty_sync_count);
+    uint64_t generation = stat64_get(&mig_stats.iteration_count);
 
     if (!cache_is_cached(XBZRLE.cache, current_addr, generation)) {
         xbzrle_counters.cache_miss++;
@@ -1079,6 +1079,10 @@ static void migration_bitmap_sync(RAMState *rs,
     RAMBlock *block;
     int64_t end_time;
 
+    if (!background) {
+        stat64_add(&mig_stats.iteration_count, 1);
+    }
+
     stat64_add(&mig_stats.dirty_sync_count, 1);
 
     if (!rs->time_last_bitmap_sync) {
@@ -1115,8 +1119,8 @@ static void migration_bitmap_sync(RAMState *rs,
         rs->num_dirty_pages_period = 0;
         rs->bytes_xfer_prev = migration_transferred_bytes();
     }
-    if (migrate_events()) {
-        uint64_t generation = stat64_get(&mig_stats.dirty_sync_count);
+    if (!background && migrate_events()) {
+        uint64_t generation = stat64_get(&mig_stats.iteration_count);
         qapi_event_send_migration_pass(generation);
     }
 }
diff --git a/qapi/migration.json b/qapi/migration.json
index b66cccf107..95b490706c 100644
--- a/qapi/migration.json
+++ b/qapi/migration.json
@@ -60,6 +60,9 @@
 #     between 0 and @dirty-sync-count * @multifd-channels.  (since
 #     7.1)
 #
+# @iteration-count: The number of iterations since migration started.
+#     (since 9.2)
+#
 # Since: 0.14
 ##
 { 'struct': 'MigrationStats',
@@ -72,7 +75,8 @@
            'multifd-bytes': 'uint64', 'pages-per-second': 'uint64',
            'precopy-bytes': 'uint64', 'downtime-bytes': 'uint64',
            'postcopy-bytes': 'uint64',
-           'dirty-sync-missed-zero-copy': 'uint64' } }
+           'dirty-sync-missed-zero-copy': 'uint64',
+           'iteration-count' : 'int' } }
 
 ##
 # @XBZRLECacheStats:
diff --git a/tests/qtest/migration-test.c b/tests/qtest/migration-test.c
index d6768d5d71..b796a90cad 100644
--- a/tests/qtest/migration-test.c
+++ b/tests/qtest/migration-test.c
@@ -278,7 +278,7 @@ static int64_t read_migrate_property_int(QTestState *who, const char *property)
 
 static uint64_t get_migration_pass(QTestState *who)
 {
-    return read_ram_property_int(who, "dirty-sync-count");
+    return read_ram_property_int(who, "iteration-count");
 }
 
 static void read_blocktime(QTestState *who)
-- 
2.39.1