[Qemu-devel] [PATCH 31/46] Postcopy: Rework migration thread for postcopy mode

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Switch to postcopy if:
   1) There's still a significant amount to transfer
   2) Postcopy is enabled
   3) It's taken longer than the time set by the parameter.

and change the cleanup at the end of migration to match.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 migration.c | 92 ++++++++++++++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 73 insertions(+), 19 deletions(-)

diff --git a/migration.c b/migration.c
index 0d567ef..c73fcfa 100644
--- a/migration.c
+++ b/migration.c
@@ -982,16 +982,40 @@ static int postcopy_start(MigrationState *ms)
 static void *migration_thread(void *opaque)
 {
     MigrationState *s = opaque;
+    /* Used by the bandwidth calcs, updated later */
     int64_t initial_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
+    /* Really, the time we started */
+    const int64_t initial_time_fixed = initial_time;
     int64_t setup_start = qemu_clock_get_ms(QEMU_CLOCK_HOST);
     int64_t initial_bytes = 0;
     int64_t max_size = 0;
     int64_t start_time = initial_time;
+    int64_t pc_start_time;
+
     bool old_vm_running = false;
+    pc_start_time = s->tunables[MIGRATION_PARAMETER_NAME_X_POSTCOPY_START_TIME];
+
+    /* The active state we expect to be in; ACTIVE or POSTCOPY_ACTIVE */
+    enum MigrationPhase current_active_type = MIG_STATE_ACTIVE;
 
     qemu_savevm_state_begin(s->file, &s->params);
 
+    if (migrate_postcopy_ram()) {
+        /* Now tell the dest that it should open it's end so it can reply */
+        qemu_savevm_send_openrp(s->file);
+
+        /* And ask it to send an ack that will make stuff easier to debug */
+        qemu_savevm_send_reqack(s->file, 1);
+
+        /* Tell the destination that we *might* want to do postcopy later;
+         * if the other end can't do postcopy it should fail now, nice and
+         * early.
+         */
+        qemu_savevm_send_postcopy_ram_advise(s->file);
+    }
+
     s->setup_time = qemu_clock_get_ms(QEMU_CLOCK_HOST) - setup_start;
+    current_active_type = MIG_STATE_ACTIVE;
     migrate_set_state(s, MIG_STATE_SETUP, MIG_STATE_ACTIVE);
 
     DPRINTF("setup complete\n");
@@ -1012,37 +1036,66 @@ static void *migration_thread(void *opaque)
                     " nonpost=%" PRIu64 ")\n",
                     pending_size, max_size, pend_post, pend_nonpost);
             if (pending_size && pending_size >= max_size) {
-                qemu_savevm_state_iterate(s->file);
+                /* Still a significant amount to transfer */
+
+                current_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
+                if (migrate_postcopy_ram() &&
+                    s->state != MIG_STATE_POSTCOPY_ACTIVE &&
+                    pend_nonpost == 0 &&
+                    (current_time >= initial_time_fixed + pc_start_time)) {
+
+                    if (!postcopy_start(s)) {
+                        current_active_type = MIG_STATE_POSTCOPY_ACTIVE;
+                    }
+
+                    continue;
+                } else {
+                    /* Just another iteration step */
+                    qemu_savevm_state_iterate(s->file);
+                }
             } else {
                 int ret;
 
-                DPRINTF("done iterating\n");
-                qemu_mutex_lock_iothread();
-                start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
-                qemu_system_wakeup_request(QEMU_WAKEUP_REASON_OTHER);
-                old_vm_running = runstate_is_running();
-
-                ret = vm_stop_force_state(RUN_STATE_FINISH_MIGRATE);
-                if (ret >= 0) {
-                    qemu_file_set_rate_limit(s->file, INT64_MAX);
-                    qemu_savevm_state_complete(s->file);
-                }
-                qemu_mutex_unlock_iothread();
-
-                if (ret < 0) {
-                    migrate_set_state(s, MIG_STATE_ACTIVE, MIG_STATE_ERROR);
-                    break;
+                DPRINTF("done iterating pending size %" PRIu64 "\n",
+                        pending_size);
+
+                if (s->state == MIG_STATE_ACTIVE) {
+                    qemu_mutex_lock_iothread();
+                    start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
+                    qemu_system_wakeup_request(QEMU_WAKEUP_REASON_OTHER);
+                    old_vm_running = runstate_is_running();
+
+                    ret = vm_stop_force_state(RUN_STATE_FINISH_MIGRATE);
+                    if (ret >= 0) {
+                        qemu_file_set_rate_limit(s->file, INT64_MAX);
+                        qemu_savevm_state_complete(s->file);
+                    }
+                    qemu_mutex_unlock_iothread();
+
+                    if (ret < 0) {
+                        migrate_set_state(s, current_active_type,
+                                          MIG_STATE_ERROR);
+                        break;
+                    }
+                } else {
+                    assert(s->state == MIG_STATE_POSTCOPY_ACTIVE);
+                    DPRINTF("postcopy end\n");
+
+                    qemu_savevm_state_postcopy_complete(s->file);
+                    DPRINTF("postcopy end after complete\n");
                 }
 
                 if (!qemu_file_get_error(s->file)) {
-                    migrate_set_state(s, MIG_STATE_ACTIVE, MIG_STATE_COMPLETED);
+                    migrate_set_state(s, current_active_type,
+                                      MIG_STATE_COMPLETED);
                     break;
                 }
             }
         }
 
         if (qemu_file_get_error(s->file)) {
-            migrate_set_state(s, MIG_STATE_ACTIVE, MIG_STATE_ERROR);
+            migrate_set_state(s, current_active_type, MIG_STATE_ERROR);
+            DPRINTF("migration_thread: file is in error state\n");
             break;
         }
         current_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
@@ -1073,6 +1126,7 @@ static void *migration_thread(void *opaque)
         }
     }
 
+    DPRINTF("migration_thread: Hit error: case\n");
     qemu_mutex_lock_iothread();
     if (s->state == MIG_STATE_COMPLETED) {
         int64_t end_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
-- 
1.9.3