[v2,7/8] iotests/129: Limit mirror job's buffer size

Commit Message

Max Reitz Jan. 13, 2021, 5:57 p.m. UTC

Issuing 'stop' on the VM drains all nodes.  If the mirror job has many
large requests in flight, this may lead to significant I/O that looks a
bit like 'stop' would make the job try to complete (which is what 129
should verify not to happen).

We can limit the I/O in flight by limiting the buffer size, so mirror
will make very little progress during the 'stop' drain.

(We do not need to do anything about commit, which has a buffer size of
512 kB by default; or backup, which goes cluster by cluster.  Once we
have asynchronous requests for backup, that will change, but then we can
fine-tune the backup job to only perform a single request on a very
small chunk, too.)

Signed-off-by: Max Reitz <[e-mail]>
Reviewed-by: Eric Blake <[e-mail]>
Reviewed-by: Vladimir Sementsov-Ogievskiy <[e-mail]>
---
 tests/qemu-iotests/129 | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Patch

diff --git a/tests/qemu-iotests/129 b/tests/qemu-iotests/129
index 7b4b6649f0..6d21470cd7 100755
--- a/tests/qemu-iotests/129
+++ b/tests/qemu-iotests/129
@@ -67,7 +67,7 @@  class TestStopWithBlockJob(iotests.QMPTestCase):
     def test_drive_mirror(self):
         self.do_test_stop("drive-mirror", device="drive0",
                           target=self.target_img, format=iotests.imgfmt,
-                          sync="full")
+                          sync="full", buf_size=65536)
 
     def test_drive_backup(self):
         self.do_test_stop("drive-backup", device="drive0",