[Intel-gfx] [PATCH i-g-t 1/3] igt/gem_sync: Exercise sync after context switch

[Antonio Argenziano]

On 15/08/18 03:26, Chris Wilson wrote:
> Quoting Antonio Argenziano (2018-08-15 00:50:43)
>>
>>
>> On 10/08/18 04:01, Chris Wilson wrote:
>>> This exercises a special case that may be of interest, waiting for a
>>> context that may be preempted in order to reduce the wait.
>>>
>>> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
>>> ---
>>> +             cycles = 0;
>>> +             elapsed = 0;
>>> +             start = gettime();
>>> +             do {
>>> +                     do {
>>> +                             double this;
>>> +
>>> +                             gem_execbuf(fd, &contexts[0].execbuf);
>>> +                             gem_execbuf(fd, &contexts[1].execbuf);
>>
>> I'm not sure where the preemption, mentioned in the commit message, is
>> coming in.
> 
> Internally. I've suggested that we reorder equivalent contexts in order
> to satisfy client waits earlier. So having created two independent
> request queues, userspace should be oblivious to the execution order.

But there isn't an assert because you don't want that to be part of the 
contract between the driver and userspace, is that correct?

Antonio

> -Chris
>