starred/qemu-qemu
1
0
Fork 0
mirror of https://github.com/qemu/qemu.git synced 2026-07-08 17:46:17 +00:00
Code Issues Packages Projects Releases Wiki Activity

migration: Calculate expected downtime on demand

Browse Source 
This value does not need to be calculated as frequent.  Only calculate it
on demand when query-migrate happened.  With that we can remove the
variable in MigrationState.

This paves way for fixing this value to include all modules (not only RAM
but others too).

Reviewed-by: Juraj Marcin <jmarcin@redhat.com>
Link: https://lore.kernel.org/r/20260421202110.306051-12-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
This commit is contained in:
Peter Xu
2026-04-21 16:21:05 -04:00
parent 474838440f
commit dd4fe8844b
2 changed files with 13 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files

25
migration/migration.c
View File

@@ -1041,6 +1041,17 @@ static bool migrate_show_downtime(MigrationState *s)
return (s->state == MIGRATION_STATUS_COMPLETED) || migration_in_postcopy();
}
/* Return expected downtime (unit: milliseconds) */
int64_t migration_downtime_calc_expected(MigrationState *s)
{
if (mig_stats.dirty_sync_count <= 1) {
return migrate_downtime_limit();
}
return mig_stats.dirty_bytes_last_sync /
migration_get_switchover_bw(s) * 1000;
}
static void populate_time_info(MigrationInfo *info, MigrationState *s)
{
info->has_status = true;
@@ -1061,7 +1072,7 @@ static void populate_time_info(MigrationInfo *info, MigrationState *s)
info->downtime = s->downtime;
} else {
info->has_expected_downtime = true;
info->expected_downtime = s->expected_downtime;
info->expected_downtime = migration_downtime_calc_expected(s);
}
}
@@ -1649,7 +1660,6 @@ int migrate_init(MigrationState *s, Error **errp)
s->mbps = 0.0;
s->pages_per_second = 0.0;
s->downtime = 0;
s->expected_downtime = 0;
s->setup_time = 0;
s->start_postcopy = false;
s->migration_thread_running = false;
@@ -3166,15 +3176,6 @@ static void migration_update_counters(MigrationState *s,
s->pages_per_second = (double) transferred_pages /
(((double) time_spent / 1000.0));
/*
* if we haven't sent anything, we don't want to
* recalculate. 10000 is a small enough number for our purposes
*/
if (mig_stats.dirty_pages_rate && transferred > 10000) {
s->expected_downtime =
mig_stats.dirty_bytes_last_sync / switchover_bw_per_ms;
}
migration_rate_reset();
update_iteration_initial_status(s);
@@ -3841,8 +3842,6 @@ void migration_start_outgoing(MigrationState *s)
bool resume = (s->state == MIGRATION_STATUS_POSTCOPY_RECOVER_SETUP);
int ret;
s->expected_downtime = migrate_downtime_limit();
if (resume) {
/* This is a resumed migration */
rate_limit = migrate_max_postcopy_bandwidth();

2
migration/migration.h
View File

@@ -359,7 +359,6 @@ struct MigrationState {
/* Timestamp when VM is down (ms) to migrate the last stuff */
int64_t downtime_start;
int64_t downtime;
int64_t expected_downtime;
bool capabilities[MIGRATION_CAPABILITY__MAX];
int64_t setup_time;
@@ -585,6 +584,7 @@ void migration_cancel(void);
void migration_populate_vfio_info(MigrationInfo *info);
void migration_reset_vfio_bytes_transferred(void);
void postcopy_temp_page_reset(PostcopyTmpPage *tmp_page);
int64_t migration_downtime_calc_expected(MigrationState *s);
/*
* Migration thread waiting for return path thread. Return non-zero if an