The background sync watcher is used to detect that if the
iteration lasts a long time, if so, trigger the background
sync.
Signed-off-by: Hyman Huang <yong.hu...@smartx.com>
---
migration/ram.c | 110 +++++++++++++++++++++++++++++++++++++++++
migration/ram.h | 3 ++
migration/trace-events | 3 ++
3 files changed, 116 insertions(+)
diff --git a/migration/ram.c b/migration/ram.c
index ca5a1b5f16..799eaa0382 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -416,6 +416,11 @@ struct RAMState {
* RAM migration.
*/
unsigned int postcopy_bmap_sync_requested;
+
+ /* Background throttle information */
+ bool background_sync_running;
+ QemuThread background_sync_thread;
+ QemuSemaphore quit_sem;
};
typedef struct RAMState RAMState;
@@ -1125,6 +1130,111 @@ static void migration_bitmap_sync(RAMState *rs,
}
}
+/*
+ * Iteration lasting more than five seconds is undesirable;
+ * launch a background dirty bitmap sync.
+ */
+#define MIGRATION_MAX_ITERATION_DURATION 5
+
+static void *migration_background_sync_watcher(void *opaque)
+{
+ RAMState *rs = opaque;
+ uint64_t iter_cnt, prev_iter_cnt = 2;
+ bool iter_cnt_unchanged = false;
+ int max_pct = migrate_max_cpu_throttle();
+
+ trace_migration_background_sync_watcher_start();
+ rcu_register_thread();
+
+ while (qatomic_read(&rs->background_sync_running)) {
+ int cur_pct = cpu_throttle_get_percentage();
+ if ((cur_pct == max_pct) || (!migration_is_active())) {
+ break;
+ }
+
+ if (qemu_sem_timedwait(&rs->quit_sem, 1000) == 0) {
+ /* We were woken by background_sync_cleanup, quit */
+ break;
+ }
+
+ /*
+ * The first iteration copies all memory anyhow and has no
+ * effect on guest performance, therefore omit it to avoid
+ * paying extra for the sync penalty.
+ */
+ iter_cnt = stat64_get(&mig_stats.iteration_count);
+ if (iter_cnt <= 1) {
+ continue;
+ }
+
+ iter_cnt_unchanged = (iter_cnt == prev_iter_cnt);
+ prev_iter_cnt = iter_cnt;
+
+ if (iter_cnt_unchanged) {
+ int64_t curr_time, iter_duration;
+
+ curr_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
+ iter_duration = curr_time - rs->time_last_bitmap_sync;
+
+ if (iter_duration >
+ MIGRATION_MAX_ITERATION_DURATION * 1000) {
+ sync_mode = RAMBLOCK_SYN_MODERN;
+ bql_lock();
+ trace_migration_background_sync();
+ WITH_RCU_READ_LOCK_GUARD() {
+ migration_bitmap_sync(rs, false, true);
+ }
+ bql_unlock();
+ }
+ }
+ }
+
+ qatomic_set(&rs->background_sync_running, 0);
+
+ rcu_unregister_thread();
+ trace_migration_background_sync_watcher_end();
+
+ return NULL;
+}
+
+void migration_background_sync_setup(void)
+{
+ RAMState *rs = ram_state;
+
+ if (!rs) {
+ return;
+ }
+
+ if (qatomic_read(&rs->background_sync_running)) {
+ return;
+ }
+
+ qemu_sem_init(&rs->quit_sem, 0);
+ qatomic_set(&rs->background_sync_running, 1);
+
+ qemu_thread_create(&rs->background_sync_thread,
+ NULL, migration_background_sync_watcher,
+ rs, QEMU_THREAD_JOINABLE);
+}
+
+void migration_background_sync_cleanup(void)
+{
+ RAMState *rs = ram_state;
+
+ if (!rs) {
+ return;
+ }
+
+ if (!qatomic_read(&rs->background_sync_running)) {
+ return;
+ }
+
+ qatomic_set(&rs->background_sync_running, 0);
+ qemu_sem_post(&rs->quit_sem);
+ qemu_thread_join(&rs->background_sync_thread);
+ qemu_sem_destroy(&rs->quit_sem);
+}
+
static void migration_bitmap_sync_precopy(RAMState *rs, bool last_stage)
{
Error *local_err = NULL;
diff --git a/migration/ram.h b/migration/ram.h
index bc0318b834..0315d22a66 100644
--- a/migration/ram.h
+++ b/migration/ram.h
@@ -93,4 +93,7 @@ void ram_write_tracking_prepare(void);
int ram_write_tracking_start(void);
void ram_write_tracking_stop(void);
+/* Migration background sync */
+void migration_background_sync_setup(void);
+void migration_background_sync_cleanup(void);
#endif
diff --git a/migration/trace-events b/migration/trace-events
index c65902f042..4f95f9fe14 100644
--- a/migration/trace-events
+++ b/migration/trace-events
@@ -92,6 +92,9 @@ qemu_file_fclose(void) ""
# ram.c
get_queued_page(const char *block_name, uint64_t tmp_offset, unsigned long
page_abs) "%s/0x%" PRIx64 " page_abs=0x%lx"
get_queued_page_not_dirty(const char *block_name, uint64_t tmp_offset,
unsigned long page_abs) "%s/0x%" PRIx64 " page_abs=0x%lx"
+migration_background_sync(void) ""
+migration_background_sync_watcher_start(void) ""
+migration_background_sync_watcher_end(void) ""
migration_bitmap_sync_start(void) ""
migration_bitmap_sync_end(uint64_t dirty_pages) "dirty_pages %" PRIu64
migration_bitmap_clear_dirty(char *str, uint64_t start, uint64_t size,
unsigned long page) "rb %s start 0x%"PRIx64" size 0x%"PRIx64" page 0x%lx"
--
2.39.1
