| Message ID | d74bc4ffb073c886bc566e7d771910db844cec1b.1726390099.git.yong.huang@smartx.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | migration: auto-converge refinements for huge VM | expand |
Hyman Huang <yong.huang@smartx.com> writes: > When VM is configured with huge memory, the current throttle logic > doesn't look like to scale, because migration_trigger_throttle() > is only called for each iteration, so it won't be invoked for a long > time if one iteration can take a long time. > > The background sync and throttle aim to fix the above issue by > synchronizing the remote dirty bitmap and triggering the throttle > once detect that iteration lasts a long time. > > This is a trade-off between synchronization overhead and CPU throttle > impact. > > Signed-off-by: Hyman Huang <yong.huang@smartx.com> > --- > migration/migration.c | 12 +++++++++++ > tests/qtest/migration-test.c | 39 ++++++++++++++++++++++++++++++++++++ > 2 files changed, 51 insertions(+) > > diff --git a/migration/migration.c b/migration/migration.c > index 055d527ff6..af8b22fa15 100644 > --- a/migration/migration.c > +++ b/migration/migration.c > @@ -1416,6 +1416,7 @@ static void migrate_fd_cleanup(MigrationState *s) > > trace_migrate_fd_cleanup(); > bql_unlock(); > + migration_background_sync_cleanup(); > if (s->migration_thread_running) { > qemu_thread_join(&s->thread); > s->migration_thread_running = false; > @@ -3263,6 +3264,7 @@ static MigIterateState migration_iteration_run(MigrationState *s) > > if ((!pending_size || pending_size < s->threshold_size) && can_switchover) { > trace_migration_thread_low_pending(pending_size); > + migration_background_sync_cleanup(); This one is redundant with the migrate_fd_cleanup() call at the end of migration_iteration_finish(). > migration_completion(s); > return MIG_ITERATE_BREAK; > } > @@ -3508,6 +3510,16 @@ static void *migration_thread(void *opaque) > ret = qemu_savevm_state_setup(s->to_dst_file, &local_err); > bql_unlock(); > > + if (!migrate_dirty_limit()) { > + /* > + * Initiate the background sync watcher in order to guarantee > + * that the CPU throttling acts appropriately. Dirty Limit > + * doesn't use CPU throttle to make guest down, so ignore that > + * case. > + */ > + migration_background_sync_setup(); > + } > + > qemu_savevm_wait_unplug(s, MIGRATION_STATUS_SETUP, > MIGRATION_STATUS_ACTIVE); > > diff --git a/tests/qtest/migration-test.c b/tests/qtest/migration-test.c > index b796a90cad..e0e94d26be 100644 > --- a/tests/qtest/migration-test.c > +++ b/tests/qtest/migration-test.c > @@ -281,6 +281,11 @@ static uint64_t get_migration_pass(QTestState *who) > return read_ram_property_int(who, "iteration-count"); > } > > +static uint64_t get_dirty_sync_count(QTestState *who) > +{ > + return read_ram_property_int(who, "dirty-sync-count"); > +} > + > static void read_blocktime(QTestState *who) > { > QDict *rsp_return; > @@ -468,6 +473,12 @@ static void migrate_ensure_converge(QTestState *who) > migrate_set_parameter_int(who, "downtime-limit", 30 * 1000); > } > > +static void migrate_ensure_iteration_last_long(QTestState *who) > +{ > + /* Set 10Byte/s bandwidth limit to make the iteration last long enough */ > + migrate_set_parameter_int(who, "max-bandwidth", 10); > +} > + > /* > * Our goal is to ensure that we run a single full migration > * iteration, and also dirty memory, ensuring that at least > @@ -2791,6 +2802,10 @@ static void test_migrate_auto_converge(void) > * so we need to decrease a bandwidth. > */ > const int64_t init_pct = 5, inc_pct = 25, max_pct = 95; > + uint64_t prev_iter_cnt = 0, iter_cnt; > + uint64_t iter_cnt_changes = 0; > + uint64_t prev_dirty_sync_cnt = 0, dirty_sync_cnt; > + uint64_t dirty_sync_cnt_changes = 0; > > if (test_migrate_start(&from, &to, uri, &args)) { > return; > @@ -2827,6 +2842,30 @@ static void test_migrate_auto_converge(void) > } while (true); > /* The first percentage of throttling should be at least init_pct */ > g_assert_cmpint(percentage, >=, init_pct); > + > + /* Make sure the iteration take a long time enough */ > + migrate_ensure_iteration_last_long(from); > + > + /* > + * End the loop when the dirty sync count or iteration count changes. > + */ > + while (iter_cnt_changes < 2 && dirty_sync_cnt_changes < 2) { > + usleep(1000 * 1000); > + iter_cnt = get_migration_pass(from); > + iter_cnt_changes += (iter_cnt != prev_iter_cnt); > + prev_iter_cnt = iter_cnt; > + > + dirty_sync_cnt = get_dirty_sync_count(from); > + dirty_sync_cnt_changes += (dirty_sync_cnt != prev_dirty_sync_cnt); > + prev_dirty_sync_cnt = dirty_sync_cnt; > + } > + > + /* > + * The dirty sync count must have changed because we are in the same > + * iteration. > + */ > + g_assert_cmpint(iter_cnt_changes , < , dirty_sync_cnt_changes); > + > /* Now, when we tested that throttling works, let it converge */ > migrate_ensure_converge(from);
diff --git a/migration/migration.c b/migration/migration.c index 055d527ff6..af8b22fa15 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -1416,6 +1416,7 @@ static void migrate_fd_cleanup(MigrationState *s) trace_migrate_fd_cleanup(); bql_unlock(); + migration_background_sync_cleanup(); if (s->migration_thread_running) { qemu_thread_join(&s->thread); s->migration_thread_running = false; @@ -3263,6 +3264,7 @@ static MigIterateState migration_iteration_run(MigrationState *s) if ((!pending_size || pending_size < s->threshold_size) && can_switchover) { trace_migration_thread_low_pending(pending_size); + migration_background_sync_cleanup(); migration_completion(s); return MIG_ITERATE_BREAK; } @@ -3508,6 +3510,16 @@ static void *migration_thread(void *opaque) ret = qemu_savevm_state_setup(s->to_dst_file, &local_err); bql_unlock(); + if (!migrate_dirty_limit()) { + /* + * Initiate the background sync watcher in order to guarantee + * that the CPU throttling acts appropriately. Dirty Limit + * doesn't use CPU throttle to make guest down, so ignore that + * case. + */ + migration_background_sync_setup(); + } + qemu_savevm_wait_unplug(s, MIGRATION_STATUS_SETUP, MIGRATION_STATUS_ACTIVE); diff --git a/tests/qtest/migration-test.c b/tests/qtest/migration-test.c index b796a90cad..e0e94d26be 100644 --- a/tests/qtest/migration-test.c +++ b/tests/qtest/migration-test.c @@ -281,6 +281,11 @@ static uint64_t get_migration_pass(QTestState *who) return read_ram_property_int(who, "iteration-count"); } +static uint64_t get_dirty_sync_count(QTestState *who) +{ + return read_ram_property_int(who, "dirty-sync-count"); +} + static void read_blocktime(QTestState *who) { QDict *rsp_return; @@ -468,6 +473,12 @@ static void migrate_ensure_converge(QTestState *who) migrate_set_parameter_int(who, "downtime-limit", 30 * 1000); } +static void migrate_ensure_iteration_last_long(QTestState *who) +{ + /* Set 10Byte/s bandwidth limit to make the iteration last long enough */ + migrate_set_parameter_int(who, "max-bandwidth", 10); +} + /* * Our goal is to ensure that we run a single full migration * iteration, and also dirty memory, ensuring that at least @@ -2791,6 +2802,10 @@ static void test_migrate_auto_converge(void) * so we need to decrease a bandwidth. */ const int64_t init_pct = 5, inc_pct = 25, max_pct = 95; + uint64_t prev_iter_cnt = 0, iter_cnt; + uint64_t iter_cnt_changes = 0; + uint64_t prev_dirty_sync_cnt = 0, dirty_sync_cnt; + uint64_t dirty_sync_cnt_changes = 0; if (test_migrate_start(&from, &to, uri, &args)) { return; @@ -2827,6 +2842,30 @@ static void test_migrate_auto_converge(void) } while (true); /* The first percentage of throttling should be at least init_pct */ g_assert_cmpint(percentage, >=, init_pct); + + /* Make sure the iteration take a long time enough */ + migrate_ensure_iteration_last_long(from); + + /* + * End the loop when the dirty sync count or iteration count changes. + */ + while (iter_cnt_changes < 2 && dirty_sync_cnt_changes < 2) { + usleep(1000 * 1000); + iter_cnt = get_migration_pass(from); + iter_cnt_changes += (iter_cnt != prev_iter_cnt); + prev_iter_cnt = iter_cnt; + + dirty_sync_cnt = get_dirty_sync_count(from); + dirty_sync_cnt_changes += (dirty_sync_cnt != prev_dirty_sync_cnt); + prev_dirty_sync_cnt = dirty_sync_cnt; + } + + /* + * The dirty sync count must have changed because we are in the same + * iteration. + */ + g_assert_cmpint(iter_cnt_changes , < , dirty_sync_cnt_changes); + /* Now, when we tested that throttling works, let it converge */ migrate_ensure_converge(from);
When VM is configured with huge memory, the current throttle logic doesn't look like to scale, because migration_trigger_throttle() is only called for each iteration, so it won't be invoked for a long time if one iteration can take a long time. The background sync and throttle aim to fix the above issue by synchronizing the remote dirty bitmap and triggering the throttle once detect that iteration lasts a long time. This is a trade-off between synchronization overhead and CPU throttle impact. Signed-off-by: Hyman Huang <yong.huang@smartx.com> --- migration/migration.c | 12 +++++++++++ tests/qtest/migration-test.c | 39 ++++++++++++++++++++++++++++++++++++ 2 files changed, 51 insertions(+)