Re: [PULL 00/11] bitmaps patches for 2020-05-26

[Eric Blake]

On 5/27/20 3:07 PM, Peter Maydell wrote:

> iotest 190 failed on freebsd:

> +++ /home/qemu/qemu-test.BE3Bvf/build/tests/qemu-iotests/190.out.bad
>   2020-05-27 15:30:50.377759533 +0000
> @@ -17,7 +17,7 @@
>   fully allocated size: 10813440
>   required size: 2199023255552
>   fully allocated size: 2199023255552
> -required size: 7012352
> +required size: 17170432
>   fully allocated size: 17170432

Thanks for the heads up.  That was on:

# No bitmap output, since no bitmaps on raw source
$QEMU_IMG measure -O qcow2 -f raw "$TEST_IMG"

and indicates that on FreeBSD, the qcow2 image is not as sparse as it is 
on other platforms.  Where Linux was able to punch holes in the 
underlying filesystem, FreeBSD did not.  But even though I'm not sure if 
that is due to file system hole granularity, choice of APIs used to 
write all-zero bitmaps, or something else, I am certain that it less 
important (the qcow2 file is still quite sparse in comparison to the 2T 
guest-visible data it is representing, even if it differs in sparseness 
between the systems).

I'll post a v2 that filters out the required size for just that command, 
as viewing a qcow2 file as if raw is unusual.

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org