Re: Slow down with: 'Make "info qom-tree" show children sorted'

[Markus Armbruster <armbru@redhat.com>]

Philippe Mathieu-Daudé <philmd@redhat.com> writes:

> On 7/7/20 6:45 AM, Thomas Huth wrote:
>> On 27/05/2020 10.47, Markus Armbruster wrote:
>>> "info qom-tree" prints children in unstable order.  This is a pain
>>> when diffing output for different versions to find change.  Print it
>>> sorted.
>>>
>>> Signed-off-by: Markus Armbruster <armbru@redhat.com>
>>> ---
>>>  qom/qom-hmp-cmds.c | 24 ++++++++++++++++--------
>>>  1 file changed, 16 insertions(+), 8 deletions(-)
>> 
>>  Hi Markus,
>> 
>> this patch causes a slow down of the qtests which becomes quite massive
>> when e.g. using the ppc64 and thourough testing. When I'm running
>> 
>> QTEST_QEMU_BINARY="ppc64-softmmu/qemu-system-ppc64" time \
>> ./tests/qtest/device-introspect-test -m slow | tail -n 10
>> 
>> the test runs for ca. 6m40s here before the patch got applied, and for
>> mor than 20 minutes after the patch got applied!

That's surprising.

> Argh, yesterday I reviewed again all the range except this patch... not
> sure why as looking at it now it is obvious.
>
>> This causes our gitlab CI to constantly fail since the patch got merged,
>> since the testing time now exceeds the 1h time limit:
>> 
>>  https://gitlab.com/qemu-project/qemu/-/pipelines/156767175
>> 
>> Sure, we can work around that problem in the CI (Alex has already a
>> patch queued), but still, is there something you could do about this
>> massive slowdown?
>
> Suggestion: add a '-u' option for unsorted mode, to use in qtests.
>
> Humans want the new behavior (default: sorted).

Last resort.  

I'll look into speeding up the sort first.

Work-around: drop -m slow until we get this sorted (pardon the pun).