qemu-iotests/199: better catch postcopy time

The test aims to test _postcopy_ migration, and wants to do some write
operations during postcopy time.

Test considers migrate status=complete event on source as start of
postcopy. This is completely wrong, completion is completion of the
whole migration process. Let's instead consider destination start as
start of postcopy, and use RESUME event for it.

Next, as migration finish, let's use migration status=complete event on
target, as such method is closer to what libvirt or another user will
do, than tracking number of dirty-bitmaps.

Finally, add a possibility to dump events for debug. And if
set debug to True, we see, that actual postcopy period is very small
relatively to the whole test duration time (~0.2 seconds to >40 seconds
for me). This means, that test is very inefficient in what it supposed
to do. Let's improve it in following commits.
Signed-off-by: NVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: NAndrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Tested-by: NEric Blake <eblake@redhat.com>
Message-Id: <20200727194236.19551-4-vsementsov@virtuozzo.com>
Signed-off-by: NEric Blake <eblake@redhat.com>

tests/qemu-iotests/199

@@ -20,17 +20,43 @@
 
 import os
 import iotests
-import time
 from iotests import qemu_img
 
+debug = False
+
 disk_a = os.path.join(iotests.test_dir, 'disk_a')
 disk_b = os.path.join(iotests.test_dir, 'disk_b')
 size = '256G'
 fifo = os.path.join(iotests.test_dir, 'mig_fifo')
 
 
+def event_seconds(event):
+    return event['timestamp']['seconds'] + \
+        event['timestamp']['microseconds'] / 1000000.0
+
+
+def event_dist(e1, e2):
+    return event_seconds(e2) - event_seconds(e1)
+
+
 class TestDirtyBitmapPostcopyMigration(iotests.QMPTestCase):
     def tearDown(self):
+        if debug:
+            self.vm_a_events += self.vm_a.get_qmp_events()
+            self.vm_b_events += self.vm_b.get_qmp_events()
+            for e in self.vm_a_events:
+                e['vm'] = 'SRC'
+            for e in self.vm_b_events:
+                e['vm'] = 'DST'
+            events = (self.vm_a_events + self.vm_b_events)
+            events = [(e['timestamp']['seconds'],
+                       e['timestamp']['microseconds'],
+                       e['vm'],
+                       e['event'],
+                       e.get('data', '')) for e in events]
+            for e in sorted(events):
+                print('{}.{:06} {} {} {}'.format(*e))
+
         self.vm_a.shutdown()
         self.vm_b.shutdown()
         os.remove(disk_a)
@@ -47,6 +73,10 @@ class TestDirtyBitmapPostcopyMigration(iotests.QMPTestCase):
         self.vm_a.launch()
         self.vm_b.launch()
 
+        # collect received events for debug
+        self.vm_a_events = []
+        self.vm_b_events = []
+
     def test_postcopy(self):
         write_size = 0x40000000
         granularity = 512
@@ -77,15 +107,13 @@ class TestDirtyBitmapPostcopyMigration(iotests.QMPTestCase):
             self.vm_a.hmp_qemu_io('drive0', 'write %d %d' % (s, chunk))
             s += 0x10000
 
-        bitmaps_cap = {'capability': 'dirty-bitmaps', 'state': True}
-        events_cap = {'capability': 'events', 'state': True}
+        caps = [{'capability': 'dirty-bitmaps', 'state': True},
+                {'capability': 'events', 'state': True}]
 
-        result = self.vm_a.qmp('migrate-set-capabilities',
-                               capabilities=[bitmaps_cap, events_cap])
+        result = self.vm_a.qmp('migrate-set-capabilities', capabilities=caps)
         self.assert_qmp(result, 'return', {})
 
-        result = self.vm_b.qmp('migrate-set-capabilities',
-                               capabilities=[bitmaps_cap])
+        result = self.vm_b.qmp('migrate-set-capabilities', capabilities=caps)
         self.assert_qmp(result, 'return', {})
 
         result = self.vm_a.qmp('migrate', uri='exec:cat>' + fifo)
@@ -94,24 +122,38 @@ class TestDirtyBitmapPostcopyMigration(iotests.QMPTestCase):
         result = self.vm_a.qmp('migrate-start-postcopy')
         self.assert_qmp(result, 'return', {})
 
-        while True:
-            event = self.vm_a.event_wait('MIGRATION')
-            if event['data']['status'] == 'completed':
-                break
+        event_resume = self.vm_b.event_wait('RESUME')
+        self.vm_b_events.append(event_resume)
 
         s = 0x8000
         while s < write_size:
             self.vm_b.hmp_qemu_io('drive0', 'write %d %d' % (s, chunk))
             s += 0x10000
 
+        match = {'data': {'status': 'completed'}}
+        event_complete = self.vm_b.event_wait('MIGRATION', match=match)
+        self.vm_b_events.append(event_complete)
+
+        # take queued event, should already been happened
+        event_stop = self.vm_a.event_wait('STOP')
+        self.vm_a_events.append(event_stop)
+
+        downtime = event_dist(event_stop, event_resume)
+        postcopy_time = event_dist(event_resume, event_complete)
+
+        # TODO: assert downtime * 10 < postcopy_time
+        if debug:
+            print('downtime:', downtime)
+            print('postcopy_time:', postcopy_time)
+
+        # Assert that bitmap migration is finished (check that successor bitmap
+        # is removed)
         result = self.vm_b.qmp('query-block')
-        while len(result['return'][0]['dirty-bitmaps']) > 1:
-            time.sleep(2)
-            result = self.vm_b.qmp('query-block')
+        assert len(result['return'][0]['dirty-bitmaps']) == 1
 
+        # Check content of migrated (and updated by new writes) bitmap
         result = self.vm_b.qmp('x-debug-block-dirty-bitmap-sha256',
                                node='drive0', name='bitmap')
-
         self.assert_qmp(result, 'return/sha256', sha256)