[PULL 26/30] Add dirty-sync-missed-zero-copy migration stat

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

From: Leonardo Bras <leobras@redhat.com>

Signed-off-by: Leonardo Bras <leobras@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Acked-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20220711211112.18951-3-leobras@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 migration/migration.c | 2 ++
 monitor/hmp-cmds.c    | 5 +++++
 qapi/migration.json   | 7 ++++++-
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/migration/migration.c b/migration/migration.c
index 7c7e529ca7..15ae48b209 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -1057,6 +1057,8 @@ static void populate_ram_info(MigrationInfo *info, MigrationState *s)
     info->ram->normal_bytes = ram_counters.normal * page_size;
     info->ram->mbps = s->mbps;
     info->ram->dirty_sync_count = ram_counters.dirty_sync_count;
+    info->ram->dirty_sync_missed_zero_copy =
+            ram_counters.dirty_sync_missed_zero_copy;
     info->ram->postcopy_requests = ram_counters.postcopy_requests;
     info->ram->page_size = page_size;
     info->ram->multifd_bytes = ram_counters.multifd_bytes;
diff --git a/monitor/hmp-cmds.c b/monitor/hmp-cmds.c
index ca98df0495..a6dc79e0d5 100644
--- a/monitor/hmp-cmds.c
+++ b/monitor/hmp-cmds.c
@@ -307,6 +307,11 @@ void hmp_info_migrate(Monitor *mon, const QDict *qdict)
             monitor_printf(mon, "postcopy ram: %" PRIu64 " kbytes\n",
                            info->ram->postcopy_bytes >> 10);
         }
+        if (info->ram->dirty_sync_missed_zero_copy) {
+            monitor_printf(mon,
+                           "Zero-copy-send fallbacks happened: %" PRIu64 " times\n",
+                           info->ram->dirty_sync_missed_zero_copy);
+        }
     }
 
     if (info->has_disk) {
diff --git a/qapi/migration.json b/qapi/migration.json
index 7586df3dea..81185d4311 100644
--- a/qapi/migration.json
+++ b/qapi/migration.json
@@ -55,6 +55,10 @@
 # @postcopy-bytes: The number of bytes sent during the post-copy phase
 #                  (since 7.0).
 #
+# @dirty-sync-missed-zero-copy: Number of times dirty RAM synchronization could
+#                               not avoid copying dirty pages. This is between
+#                               0 and @dirty-sync-count * @multifd-channels.
+#                               (since 7.1)
 # Since: 0.14
 ##
 { 'struct': 'MigrationStats',
@@ -65,7 +69,8 @@
            'postcopy-requests' : 'int', 'page-size' : 'int',
            'multifd-bytes' : 'uint64', 'pages-per-second' : 'uint64',
            'precopy-bytes' : 'uint64', 'downtime-bytes' : 'uint64',
-           'postcopy-bytes' : 'uint64' } }
+           'postcopy-bytes' : 'uint64',
+           'dirty-sync-missed-zero-copy' : 'uint64' } }
 
 ##
 # @XBZRLECacheStats:
-- 
2.36.1