Re: [igt-dev] [PATCH i-g-t] i915/gem_exec_schedule: Check deps along implicit inter-engine semaphores

[Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>]

On 4/24/19 8:47 AM, Chris Wilson wrote:
> Given an implicit semaphore from one engine to the next, check that if
> we skip the wait on that semaphore the following batch although
> submitted early (as it depends along the single engine timeline) is not
> executed ahead of its dependency.
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
> Cc: Matthew Brost <matthew.brost@intel.com>

Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>

some nitpicks below.

> ---
> Make sure there is actually a semaphore (read-read doesn't generate an
> interengine dependency!)
> ---
>   tests/i915/gem_exec_schedule.c | 75 ++++++++++++++++++++++++++++++++++
>   1 file changed, 75 insertions(+)
> 
> diff --git a/tests/i915/gem_exec_schedule.c b/tests/i915/gem_exec_schedule.c
> index 3590b739a..a6b74b3b6 100644
> --- a/tests/i915/gem_exec_schedule.c
> +++ b/tests/i915/gem_exec_schedule.c
> @@ -603,6 +603,79 @@ static void semaphore_resolve(int i915)
>   	gem_context_destroy(i915, outer);
>   }
>   
> +static void semaphore_noskip(int i915)
> +{
> +	unsigned int engine, other;
> +	uint32_t ctx;
> +
> +	igt_assert(intel_get_drm_devid(i915) >= 8);

I would move this to igt_require since the subtest_group only requires 
scheduler & priority and even if we currently don't enable those 
pre-gen8 I don't think we can assume we never will.

> +
> +	ctx = gem_context_create(i915);
> +
> +	for_each_physical_engine(i915, engine) {
> +	for_each_physical_engine(i915, other) {

Is it worth hiding the double loop in its own macro? e.g.:

for_each_physical_engine_pair(i915, engine1, engine2)

> +		struct drm_i915_gem_exec_object2 obj[3];
> +		struct drm_i915_gem_execbuffer2 eb;
> +		igt_spin_t *chain, *spin;
> +		uint32_t handle, cancel;
> +		uint32_t *cs, *map;
> +
> +		if (other == engine || !gem_can_store_dword(i915, other))
> +			continue;
> +
> +		chain = __igt_spin_new(i915, .engine = engine);
> +
> +		spin = __igt_spin_new(i915, .engine = other);
> +		igt_spin_end(spin); /* we just want its address for later */
> +		gem_sync(i915, spin->handle);
> +		igt_spin_reset(spin);
> +
> +		handle = gem_create(i915, 4096);
> +		cs = map = gem_mmap__cpu(i915, handle, 0, 4096, PROT_WRITE);
> +
> +		/* Cancel the following spinner */
> +		*cs++ = MI_STORE_DWORD_IMM;
> +		*cs++ = spin->obj[1].offset + offset_in_page(spin->condition);
> +		*cs++ = 0;
> +		*cs++ = MI_BATCH_BUFFER_END;
> +
> +		*cs++ = MI_BATCH_BUFFER_END;
> +		munmap(map, 4096);
> +
> +		memset(obj, 0, sizeof(obj));
> +		obj[0] = chain->obj[1];
> +		obj[0].flags |= EXEC_OBJECT_WRITE;
> +		obj[1] = spin->obj[1];
> +		obj[2].handle = handle;
> +		memset(&eb, 0, sizeof(eb));
> +		eb.buffer_count = 3;
> +		eb.buffers_ptr = to_user_pointer(obj);
> +		eb.rsvd1 = ctx;
> +		eb.flags = other;
> +		gem_execbuf(i915, &eb);
> +
> +		memset(obj, 0, sizeof(obj));
> +		obj[0].handle = handle;
> +		obj[0].flags = EXEC_OBJECT_WRITE;
> +		obj[1] = spin->obj[1];
> +		memset(&eb, 0, sizeof(eb));
> +		eb.buffer_count = 2;
> +		eb.buffers_ptr = to_user_pointer(obj);
> +		eb.flags = other;
> +		gem_execbuf(i915, &eb);
> +
> +		igt_spin_set_timeout(chain, NSEC_PER_SEC / 100);
> +		gem_sync(i915, spin->handle); /* To hang unless cancel runs! */
> +
> +		gem_close(i915, handle);
> +		igt_spin_free(i915, spin);
> +		igt_spin_free(i915, chain);
> +	}
> +	}
> +
> +	gem_context_destroy(i915, ctx);
> +}
> +
>   static void reorder(int fd, unsigned ring, unsigned flags)
>   #define EQUAL 1
>   {
> @@ -1592,6 +1665,8 @@ igt_main
>   			semaphore_codependency(fd);
>   		igt_subtest("semaphore-resolve")
>   			semaphore_resolve(fd);

semaphore_resolve isn't merged yet ;)

Daniele

> +		igt_subtest("semaphore-noskip")
> +			semaphore_noskip(fd);
>   
>   		igt_subtest("smoketest-all")
>   			smoketest(fd, ALL_ENGINES, 30);
> 
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