ww-mutex performance tests?

[Christian König]

Am 04.04.2018 um 20:02 schrieb Daniel Vetter:
> On Tue, Apr 3, 2018 at 10:37 AM, Maarten Lankhorst
> <maarten.lankhorst at linux.intel.com> wrote:
>> Op 02-04-18 om 19:49 schreef Thomas Hellstrom:
>>> Maarten, Daniel,
>>>
>>> Do we have any ww-mutex performance tests somewhere that can be used to test the impact of implementation details on various locking scenarios?
>>>
>>> Thanks,
>>>
>>> /Thomas
>>>
>>>
>> The thing that comes to my mind are some of the kms_cursor_legacy tests that have been proven to be sensitive to locking issues before.
>> All subtests with (pipe-*/all-pipes)-(single/forked/torture)-(bo/move) try to do cursor updates as fast as possible, and report how many updates have been done.
> AMD folks have a bunch of tests to exercise their CS paths I think,
> that should be interesting for the multi-ww_mutex/backoff paths,
> adding Christian et al.

Well not a dedicated test for this, but at least I usually run glmark 
with thread offloading disabled to measure the command submission overhead.

Except for the usual stuff like copying things from userspace the last 
time I looked our command submission overhead was dominated by work done 
for individual BOs.

Not sure how much of that accounts for locking the ww_mutex of the BOs, 
but I would guess it is quite a bit.

Christian.

> -Daniel