[igt-dev] [PATCH i-g-t] tests/gem_exec_alignment.c: Update to be completable in a rational time.

[Grzegorzek, Dominik]

On Wed, 2020-02-12 at 10:02 +0000, Chris Wilson wrote:
> Quoting Dominik Grzegorzek (2020-02-12 09:14:01)
> > +       /*
> > +        * Due to the high complexity of searching holes in virtual
> > memory,
> > +        * number of objects has to be limited. The algorithm for
> > each alignment
> > +        * performs execbuffer multiple times and doubles number of
> > objects
> > +        * in every iteration till timeout is reached.
> > +        **/
> >         for (alignment = 4096; alignment < gtt_size; alignment <<=
> > 1) {
> > -               for (i = 0; i < count; i++)
> > -                       execobj[i].alignment = alignment;
> > +               alignment_set_timeout(TIMEOUT);
> > +               clock_gettime(CLOCK_MONOTONIC, &start);
> 
> I was thinking we made the timeout global and just run the test for a
> maximum of N secs and see how far into the alignment loop we get?
> 
> There's no reason to believe that higher power of two alignments
> provide
> any different path coverage, just as noted we find ourselves in
> increasingly fragmented virtual space. If you want a challenge,
> supplement this with a priority-inversion test case... (Where a low
> priority client can create a mess in their own address space, causing
> a
> delay [>10ms] of a high priority client. It's a clear and present
> bug.)
> -Chris
Is that priority-inversion test case cricial for you? What about
just making the timout global for now? 
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