diff mbox series

[v3,08/10] iotests/129: Limit mirror job's buffer size

Message ID 20210114170304.87507-9-mreitz@redhat.com (mailing list archive)
State New, archived
Headers show
Series iotests: Fix 129 and expand 297’s reach | expand

Commit Message

Max Reitz Jan. 14, 2021, 5:03 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 <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 tests/qemu-iotests/129 | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Willian Rampazzo Jan. 15, 2021, 2:49 p.m. UTC | #1 
On Thu, Jan 14, 2021 at 2:37 PM Max Reitz <mreitz@redhat.com> wrote:
>
> 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 <mreitz@redhat.com>
> Reviewed-by: Eric Blake <eblake@redhat.com>
> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>  tests/qemu-iotests/129 | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>

Reviewed-by: Willian Rampazzo <willianr@redhat.com>
diff mbox series

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",