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migration: Fix qmp_query_migrate mbps value

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The QMP command query_migrate might see incorrect throughput numbers
if it runs after we've set the migration completion status but before
migration_calculate_complete() has updated s->total_time and s->mbps.

The migration status would show COMPLETED, but the throughput value
would be the one from the last iteration and not the one from the
whole migration. This will usually be a larger value due to the time
period being smaller (one iteration).

Move migration_calculate_complete() earlier so that the status
MIGRATION_STATUS_COMPLETED is only emitted after the final counters
update. Keep everything under the BQL so the QMP thread sees the
updates as atomic.

Rename migration_calculate_complete to migration_completion_end to
reflect its new purpose of also updating s->state.

Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240226143335.14282-1-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>
This commit is contained in:
Fabiano Rosas 2024-02-26 11:33:35 -03:00 committed by Peter Xu
parent cbdafc1b34
commit 63f64d77f0
1 changed files with 14 additions and 9 deletions
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23
migration/migration.c
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@ -107,6 +107,7 @@ static int migration_maybe_pause(MigrationState *s,
int new_state);
static void migrate_fd_cancel(MigrationState *s);
static bool close_return_path_on_source(MigrationState *s);
static void migration_completion_end(MigrationState *s);
static void migration_downtime_start(MigrationState *s)
{
@ -2787,8 +2788,7 @@ static void migration_completion(MigrationState *s)
migrate_set_state(&s->state, MIGRATION_STATUS_ACTIVE,
MIGRATION_STATUS_COLO);
} else {
migrate_set_state(&s->state, current_active_state,
MIGRATION_STATUS_COMPLETED);
migration_completion_end(s);
}
return;
@ -2825,8 +2825,7 @@ static void bg_migration_completion(MigrationState *s)
goto fail;
}
migrate_set_state(&s->state, current_active_state,
MIGRATION_STATUS_COMPLETED);
migration_completion_end(s);
return;
fail:
@ -3028,18 +3027,28 @@ static MigThrError migration_detect_error(MigrationState *s)
}
}
static void migration_calculate_complete(MigrationState *s)
static void migration_completion_end(MigrationState *s)
{
uint64_t bytes = migration_transferred_bytes();
int64_t end_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
int64_t transfer_time;
/*
* Take the BQL here so that query-migrate on the QMP thread sees:
* - atomic update of s->total_time and s->mbps;
* - correct ordering of s->mbps update vs. s->state;
*/
bql_lock();
migration_downtime_end(s);
s->total_time = end_time - s->start_time;
transfer_time = s->total_time - s->setup_time;
if (transfer_time) {
s->mbps = ((double) bytes * 8.0) / transfer_time / 1000;
}
migrate_set_state(&s->state, s->state,
MIGRATION_STATUS_COMPLETED);
bql_unlock();
}
static void update_iteration_initial_status(MigrationState *s)
@ -3186,7 +3195,6 @@ static void migration_iteration_finish(MigrationState *s)
bql_lock();
switch (s->state) {
case MIGRATION_STATUS_COMPLETED:
migration_calculate_complete(s);
runstate_set(RUN_STATE_POSTMIGRATE);
break;
case MIGRATION_STATUS_COLO:
@ -3230,9 +3238,6 @@ static void bg_migration_iteration_finish(MigrationState *s)
bql_lock();
switch (s->state) {
case MIGRATION_STATUS_COMPLETED:
migration_calculate_complete(s);
break;
case MIGRATION_STATUS_ACTIVE:
case MIGRATION_STATUS_FAILED:
case MIGRATION_STATUS_CANCELLED: