[PATCH 3/5] migration: Add a tracepoint for the downtime stats

[Joao Martins <joao.m.martins@oracle.com>]

To facilitate understanding of what constitutes downtime, add
a tracepoint that gives the downtime breakdown throughout all
steps of switchover.

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
---
 migration/migration.c  | 34 ++++++++++++++++++++++++++++++++++
 migration/trace-events |  1 +
 2 files changed, 35 insertions(+)

diff --git a/migration/migration.c b/migration/migration.c
index d06840024a1e..4b5bed3eb09b 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -893,6 +893,34 @@ static bool migrate_show_downtime(MigrationState *s)
     return (s->state == MIGRATION_STATUS_COMPLETED) || migration_in_postcopy();
 }
 
+static int64_t migrate_get_downtime_stop(MigrationState *s)
+{
+    return migration_get_timestamp(MIGRATION_DOWNTIME_STOP) -
+        migration_get_timestamp(MIGRATION_DOWNTIME_START);
+}
+
+static int64_t migrate_get_downtime_precopy_iterable(MigrationState *s)
+{
+    return migration_get_timestamp(MIGRATION_DOWNTIME_PRECOPY_ITERABLE) -
+         migration_get_timestamp(MIGRATION_DOWNTIME_STOP);
+}
+
+static int64_t migrate_get_downtime_precopy_noniterable(MigrationState *s)
+{
+    return migration_get_timestamp(MIGRATION_DOWNTIME_PRECOPY_NONITERABLE) -
+           migration_get_timestamp(MIGRATION_DOWNTIME_PRECOPY_ITERABLE);
+}
+
+static int64_t migrate_get_downtime_resume_rp(MigrationState *s)
+{
+    if (migrate_return_path()) {
+        return migration_get_timestamp(MIGRATION_DOWNTIME_RESUME_RETURN_PATH) -
+               migration_get_timestamp(MIGRATION_DOWNTIME_PRECOPY_NONITERABLE);
+    }
+
+    return 0;
+}
+
 static void populate_time_info(MigrationInfo *info, MigrationState *s)
 {
     info->has_status = true;
@@ -2689,6 +2717,12 @@ static void migration_calculate_complete(MigrationState *s)
          * postcopy, downtime is calculated during postcopy_start().
          */
         s->downtime = end_time - migration_get_timestamp(MIGRATION_DOWNTIME_START);
+
+        trace_source_downtime_stats(s->downtime,
+                                    migrate_get_downtime_stop(s),
+                                    migrate_get_downtime_precopy_iterable(s),
+                                    migrate_get_downtime_precopy_noniterable(s),
+                                    migrate_get_downtime_resume_rp(s));
     }
 
     transfer_time = s->total_time - s->setup_time;
diff --git a/migration/trace-events b/migration/trace-events
index 4666f19325e7..163dc74bc49a 100644
--- a/migration/trace-events
+++ b/migration/trace-events
@@ -189,6 +189,7 @@ migrate_transferred(uint64_t transferred, uint64_t time_spent, uint64_t bandwidt
 process_incoming_migration_co_end(int ret, int ps) "ret=%d postcopy-state=%d"
 process_incoming_migration_co_postcopy_end_main(void) ""
 postcopy_preempt_enabled(bool value) "%d"
+source_downtime_stats(int64_t downtime, int64_t stop, int64_t iterable, int64_t non_iterable, int64_t resume_rp) "downtime %"PRIi64": stop %"PRIi64" iterable %"PRIi64" non_iterable %"PRIi64" resume-rp %"PRIi64
 
 # migration-stats
 migration_transferred_bytes(uint64_t qemu_file, uint64_t multifd) "qemu_file %" PRIu64 " multifd %" PRIu64
-- 
2.39.3