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Re: [PATCH 6/7] iotests/129: Limit mirror job's buffer size
From: |
Eric Blake |
Subject: |
Re: [PATCH 6/7] iotests/129: Limit mirror job's buffer size |
Date: |
Wed, 13 Jan 2021 10:03:25 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 |
On 1/13/21 8:06 AM, Max Reitz 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 the job is being drained.
>
> 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>
> ---
> tests/qemu-iotests/129 | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
Reviewed-by: Eric Blake <eblake@redhat.com>
>
> diff --git a/tests/qemu-iotests/129 b/tests/qemu-iotests/129
> index e6753c90ef..c3ad584ba2 100755
> --- a/tests/qemu-iotests/129
> +++ b/tests/qemu-iotests/129
> @@ -69,7 +69,7 @@ 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",
>
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
- Re: [PATCH 4/7] iotests/129: Use throttle node, (continued)
[PATCH 2/7] iotests/129: Remove test images in tearDown(), Max Reitz, 2021/01/13
[PATCH 7/7] iotests/129: Clean up pylint and mypy complaints, Max Reitz, 2021/01/13
[PATCH 6/7] iotests/129: Limit mirror job's buffer size, Max Reitz, 2021/01/13
Re: [PATCH 0/7] iotests/129: Fix it, Vladimir Sementsov-Ogievskiy, 2021/01/13
Re: [PATCH 0/7] iotests/129: Fix it, Kevin Wolf, 2021/01/13