Re: [PATCH igt 03/10] igt/gem_ctx_switch: Exercise all engines at once

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 28/07/2017 13:08, Chris Wilson wrote:
> Just a small variant to apply a continuous context-switch load to all
> engines.
> ---
>   tests/gem_ctx_switch.c | 80 ++++++++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 80 insertions(+)
> 
> diff --git a/tests/gem_ctx_switch.c b/tests/gem_ctx_switch.c
> index b6ea71cf..df22efec 100644
> --- a/tests/gem_ctx_switch.c
> +++ b/tests/gem_ctx_switch.c
> @@ -140,6 +140,81 @@ static void single(int fd, uint32_t handle,
>   		gem_context_destroy(fd, contexts[n]);
>   }
>   
> +static void all(int fd, uint32_t handle, unsigned flags, int timeout)
> +{
> +	struct drm_i915_gem_execbuffer2 execbuf;
> +	struct drm_i915_gem_exec_object2 obj[2];
> +	unsigned int engine[16], e;

Need to add MAX_ENGINES somewhere in lib/ for maintainability.

> +	const char *name[16];
> +	uint32_t contexts[64];
> +	unsigned int nengine;
> +	int n;
> +
> +	nengine = 0;
> +	for_each_engine(fd, e) {
> +		if (e == 0 || e == I915_EXEC_BSD)
> +			continue;

Engine discrimination! :) Why? BSD1 won't work except on large GTs.

Also, if we cannot agree to drop I915_EXEC_DEFAULT from the 
for_each_engine list, I think we at least need to stop the "e == 0" 
magic which is sprinkled around the tests now. Even though this very 
fact demonstrates having it in a list is most often not what is wanted.

Not sure exactly what to suggest as an alternative. for_each_hw_engine? 
real engine? gt engine?

> +
> +		engine[nengine] = e;
> +		name[nengine] = e__->name;
> +		nengine++;
> +	}
> +	igt_require(nengine);
> +
> +	igt_require(__gem_context_create(fd, &contexts[0]) == 0);

Feels to opaque - should we pencil in adding of 
igt_require_context_support or something?

> +	for (n = 1; n < 64; n++)
> +		contexts[n] = gem_context_create(fd);
> +
> +	memset(obj, 0, sizeof(obj));
> +	obj[1].handle = handle;
> +
> +	memset(&execbuf, 0, sizeof(execbuf));
> +	execbuf.buffers_ptr = to_user_pointer(obj + 1);
> +	execbuf.buffer_count = 1;
> +	execbuf.rsvd1 = contexts[0];
> +	execbuf.flags |= LOCAL_I915_EXEC_HANDLE_LUT;
> +	execbuf.flags |= LOCAL_I915_EXEC_NO_RELOC;
> +	igt_require(__gem_execbuf(fd, &execbuf) == 0);
> +	if (__gem_execbuf(fd, &execbuf)) {

Why the same execbuf two times in a row?

> +		execbuf.flags = 0;
> +		gem_execbuf(fd, &execbuf);
> +	}
> +	gem_sync(fd, handle);

What is the purpose of exercising context[0] before the main loop below?

> +	execbuf.buffers_ptr = to_user_pointer(obj);
> +	execbuf.buffer_count = 2;
> +
> +	igt_fork(child, nengine) {
> +		struct timespec start, now;
> +		unsigned int count = 0;
> +
> +		obj[0].handle = gem_create(fd, 4096);
> +		execbuf.flags |= engine[child];
> +		gem_execbuf(fd, &execbuf);
> +		gem_sync(fd, obj[0].handle);
> +
> +		clock_gettime(CLOCK_MONOTONIC, &start);
> +		do {
> +			for (int loop = 0; loop < 64; loop++) {
> +				execbuf.rsvd1 = contexts[loop % 64];
> +				gem_execbuf(fd, &execbuf);
> +			}
> +			count += 64;
> +			clock_gettime(CLOCK_MONOTONIC, &now);
> +		} while (elapsed(&start, &now) < timeout);
> +		gem_sync(fd, obj[0].handle);
> +		clock_gettime(CLOCK_MONOTONIC, &now);
> +		gem_close(fd, obj[0].handle);
> +
> +		igt_info("[%d] %s: %'u cycles: %.3fus%s\n",
> +			 child, name[child], count, elapsed(&start, &now)*1e6 / count,
> +			 flags & INTERRUPTIBLE ? " (interruptible)" : "");
> +	}
> +	igt_waitchildren();
> +
> +	for (n = 0; n < 64; n++)
> +		gem_context_destroy(fd, contexts[n]);
> +}
> +
>   igt_main
>   {
>   	const int ncpus = sysconf(_SC_NPROCESSORS_ONLN);
> @@ -177,6 +252,11 @@ igt_main
>   			single(fd, light, e, INTERRUPTIBLE, ncpus, 150);
>   	}
>   
> +	igt_subtest("basic-all")
> +		all(fd, light, 0, 20);
> +	igt_subtest("basic-all-heavy")
> +		all(fd, heavy, 0, 20);
> +
>   	igt_fixture {
>   		igt_stop_hang_detector();
>   		gem_close(fd, heavy);
> 

Regards,

Tvrtko
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