Re: [Qemu-devel] [PATCH 08/21] backup: skip unallocated clusters for full mode

[Fam Zheng]

On Tue, 01/24 12:18, Vladimir Sementsov-Ogievskiy wrote:
> 24.01.2017 10:59, Fam Zheng wrote:
> > On Fri, 12/23 17:28, Vladimir Sementsov-Ogievskiy wrote:
> > > diff --git a/tests/qemu-iotests/055 b/tests/qemu-iotests/055
> > > index 1d3fd04..388b7b2 100755
> > > --- a/tests/qemu-iotests/055
> > > +++ b/tests/qemu-iotests/055
> > > @@ -30,6 +30,7 @@ target_img = os.path.join(iotests.test_dir, 
> > > 'target.img')
> > >   blockdev_target_img = os.path.join(iotests.test_dir, 
> > > 'blockdev-target.img')
> > >   image_len = 64 * 1024 * 1024 # MB
> > > +pause_write = '3M'
> > >   def setUpModule():
> > >       qemu_img('create', '-f', iotests.imgfmt, test_img, str(image_len))
> > > @@ -39,6 +40,7 @@ def setUpModule():
> > >       qemu_io('-f', iotests.imgfmt, '-c', 'write -P0xd5 1M 32k', test_img)
> > >       qemu_io('-f', iotests.imgfmt, '-c', 'write -P0xdc 32M 124k', 
> > > test_img)
> > >       qemu_io('-f', iotests.imgfmt, '-c', 'write -P0x33 67043328 64k', 
> > > test_img)
> > > +    qemu_io('-f', iotests.imgfmt, '-c', 'write -P0xdc 40M ' + 
> > > pause_write, test_img)
> > What does this iotest change do?
> 
> Without this backup block-job finishes before the next query to it from test
> and test fails. This is a wide problem I suffer of on the way of backup
> improvement and it should have better solution then adjusting amount of data
> being copied...

You can use blkdebug to pause I/O before querying the block job, or simply
throttle it down.

Fam