[PULL 05/24] qemu-iotests/199: improve performance: set bitmap by discard

[Eric Blake <eblake@redhat.com>]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

Discard dirties dirty-bitmap as well as write, but works faster. Let's
use it instead.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Tested-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200727194236.19551-5-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 tests/qemu-iotests/199 | 31 ++++++++++++++++++++-----------
 1 file changed, 20 insertions(+), 11 deletions(-)

diff --git a/tests/qemu-iotests/199 b/tests/qemu-iotests/199
index dd6044768c76..190e820b8408 100755
--- a/tests/qemu-iotests/199
+++ b/tests/qemu-iotests/199
@@ -67,8 +67,10 @@ class TestDirtyBitmapPostcopyMigration(iotests.QMPTestCase):
         os.mkfifo(fifo)
         qemu_img('create', '-f', iotests.imgfmt, disk_a, size)
         qemu_img('create', '-f', iotests.imgfmt, disk_b, size)
-        self.vm_a = iotests.VM(path_suffix='a').add_drive(disk_a)
-        self.vm_b = iotests.VM(path_suffix='b').add_drive(disk_b)
+        self.vm_a = iotests.VM(path_suffix='a').add_drive(disk_a,
+                                                          'discard=unmap')
+        self.vm_b = iotests.VM(path_suffix='b').add_drive(disk_b,
+                                                          'discard=unmap')
         self.vm_b.add_incoming("exec: cat '" + fifo + "'")
         self.vm_a.launch()
         self.vm_b.launch()
@@ -78,7 +80,7 @@ class TestDirtyBitmapPostcopyMigration(iotests.QMPTestCase):
         self.vm_b_events = []

     def test_postcopy(self):
-        write_size = 0x40000000
+        discard_size = 0x40000000
         granularity = 512
         chunk = 4096

@@ -86,25 +88,32 @@ class TestDirtyBitmapPostcopyMigration(iotests.QMPTestCase):
                                name='bitmap', granularity=granularity)
         self.assert_qmp(result, 'return', {})

+        result = self.vm_a.qmp('x-debug-block-dirty-bitmap-sha256',
+                               node='drive0', name='bitmap')
+        empty_sha256 = result['return']['sha256']
+
         s = 0
-        while s < write_size:
-            self.vm_a.hmp_qemu_io('drive0', 'write %d %d' % (s, chunk))
+        while s < discard_size:
+            self.vm_a.hmp_qemu_io('drive0', 'discard %d %d' % (s, chunk))
             s += 0x10000
         s = 0x8000
-        while s < write_size:
-            self.vm_a.hmp_qemu_io('drive0', 'write %d %d' % (s, chunk))
+        while s < discard_size:
+            self.vm_a.hmp_qemu_io('drive0', 'discard %d %d' % (s, chunk))
             s += 0x10000

         result = self.vm_a.qmp('x-debug-block-dirty-bitmap-sha256',
                                node='drive0', name='bitmap')
         sha256 = result['return']['sha256']

+        # Check, that updating the bitmap by discards works
+        assert sha256 != empty_sha256
+
         result = self.vm_a.qmp('block-dirty-bitmap-clear', node='drive0',
                                name='bitmap')
         self.assert_qmp(result, 'return', {})
         s = 0
-        while s < write_size:
-            self.vm_a.hmp_qemu_io('drive0', 'write %d %d' % (s, chunk))
+        while s < discard_size:
+            self.vm_a.hmp_qemu_io('drive0', 'discard %d %d' % (s, chunk))
             s += 0x10000

         caps = [{'capability': 'dirty-bitmaps', 'state': True},
@@ -126,8 +135,8 @@ class TestDirtyBitmapPostcopyMigration(iotests.QMPTestCase):
         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))
+        while s < discard_size:
+            self.vm_b.hmp_qemu_io('drive0', 'discard %d %d' % (s, chunk))
             s += 0x10000

         match = {'data': {'status': 'completed'}}
-- 
2.27.0