Qemu_savevm_state_cleanup() takes about 300ms in my ram migration tests
with a 8U24G vm(20G is really occupied), the main cost comes from
KVM_SET_USER_MEMORY_REGION ioctl when mem.memory_size = 0 in
kvm_set_user_memory_region(). In kmod, the main cost is
kvm_zap_obsolete_pages(), which traverses the active_mmu_pages list to
zap the unsync sptes.
I think it can be optimized:
(1) source vm will be destroyed if the migration is successfully done,
so the resources will be cleanuped automatically by the system
(2) delay the cleanup if the migration failed
Signed-off-by: Jay Zhou <jianjay.z...@huawei.com>
---
migration/migration.c | 16 +++++++++-------
qmp.c | 10 ++++++++++
2 files changed, 19 insertions(+), 7 deletions(-)
diff --git a/migration/migration.c b/migration/migration.c
index a0db40d..72832be 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -1877,6 +1877,15 @@ static void *migration_thread(void *opaque)
if (qemu_file_get_error(s->to_dst_file)) {
migrate_set_state(&s->state, current_active_state,
MIGRATION_STATUS_FAILED);
+ /*
+ * The resource has been allocated by migration will be reused in
+ * COLO process, so don't release them.
+ */
+ if (!enable_colo) {
+ qemu_mutex_lock_iothread();
+ qemu_savevm_state_cleanup();
+ qemu_mutex_unlock_iothread();
+ }
trace_migration_thread_file_err();
break;
}
@@ -1916,13 +1925,6 @@ static void *migration_thread(void *opaque)
end_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
qemu_mutex_lock_iothread();
- /*
- * The resource has been allocated by migration will be reused in COLO
- * process, so don't release them.
- */
- if (!enable_colo) {
- qemu_savevm_state_cleanup();
- }
if (s->state == MIGRATION_STATUS_COMPLETED) {
uint64_t transferred_bytes = qemu_ftell(s->to_dst_file);
s->total_time = end_time - s->total_time;
diff --git a/qmp.c b/qmp.c
index b86201e..0e68eaa 100644
--- a/qmp.c
+++ b/qmp.c
@@ -37,6 +37,8 @@
#include "qom/object_interfaces.h"
#include "hw/mem/pc-dimm.h"
#include "hw/acpi/acpi_dev_interface.h"
+#include "migration/migration.h"
+#include "migration/savevm.h"
NameInfo *qmp_query_name(Error **errp)
{
@@ -200,6 +202,14 @@ void qmp_cont(Error **errp)
if (runstate_check(RUN_STATE_INMIGRATE)) {
autostart = 1;
} else {
+ /*
+ * Delay the cleanup to reduce the downtime of migration.
+ * The resource has been allocated by migration will be reused
+ * in COLO process, so don't release them.
+ */
+ if (runstate_check(RUN_STATE_POSTMIGRATE) && !migrate_colo_enabled()) {
+ qemu_savevm_state_cleanup();
+ }
vm_start();
}
}
--
1.8.3.1
