[igt-dev] [PATCH i-g-t 2/2] tests/gem_exec_nop: Remove submission batching

[Chris Wilson]

Quoting Janusz Krzysztofik (2020-05-08 14:56:31)
>  static double nop_on_ring(int fd, uint32_t handle,
>                           const struct intel_execution_engine2 *e, int timeout,
> -                         unsigned long *out)
> +                         unsigned long *count)
>  {
>         struct drm_i915_gem_execbuffer2 execbuf;
>         struct drm_i915_gem_exec_object2 obj;
>         struct timespec start, now;
> -       unsigned long count;
> +       unsigned long total;
> +
> +       igt_assert(*count);
>  
>         memset(&obj, 0, sizeof(obj));
>         obj.handle = handle;
> @@ -93,18 +95,18 @@ static double nop_on_ring(int fd, uint32_t handle,
>         }
>         intel_detect_and_clear_missed_interrupts(fd);
>  
> -       count = 0;
> +       total = 0;
>         clock_gettime(CLOCK_MONOTONIC, &start);
>         do {
> -               for (int loop = 0; loop < 1024; loop++)
> +               for (int loop = 0; loop < *count; loop++)

This unnerves me. I expect to get this wrong when writing new callers.

There's no great reason to even have 1024 here, we can survive with
doing clock_gettime() every iteration, and just accept it as part of the
systematic cost.

>                         gem_execbuf(fd, &execbuf);
>  
> -               count += 1024;
> +               total += *count;
>                 clock_gettime(CLOCK_MONOTONIC, &now);
>         } while (elapsed(&start, &now) < timeout);
>         igt_assert_eq(intel_detect_and_clear_missed_interrupts(fd), 0);
>  
> -       *out = count;
> +       *count = total;
>         return elapsed(&start, &now);