Re: [igt-dev] [Intel-gfx] [PATCH i-g-t] i915/gem_exec_balance: Check chain of submit dependencies

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

On 27/11/2019 14:50, Chris Wilson wrote:
> Check that the submit fence couples into the dependency chain so that
> the bonded pair cannot over take any of the earlier requests.
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> ---
>   tests/i915/gem_exec_balancer.c | 88 ++++++++++++++++++++++++++++++++++
>   1 file changed, 88 insertions(+)
> 
> diff --git a/tests/i915/gem_exec_balancer.c b/tests/i915/gem_exec_balancer.c
> index 86028cfdd..ff5bd0134 100644
> --- a/tests/i915/gem_exec_balancer.c
> +++ b/tests/i915/gem_exec_balancer.c
> @@ -855,6 +855,91 @@ static void bonded_slice(int i915)
>   	munmap(stop, 4096);
>   }
>   
> +static void bonded_chain(int i915)
> +{
> +	struct drm_i915_gem_exec_object2 batch = {
> +		.handle = batch_create(i915),
> +	};
> +	uint32_t ctx;
> +
> +	/*
> +	 * Given batches A, B and B', where B and B' are a bonded pair, with
> +	 * B' depending on B with a submit fence and B depending on A as
> +	 * an ordinary fence; prove B' cannot complete before A.
> +	 */
> +
> +	ctx = gem_context_create(i915);
> +
> +	for (int class = 0; class < 32; class++) {
> +		struct i915_engine_class_instance *siblings;
> +		struct drm_i915_gem_execbuffer2 execbuf = {
> +			.buffers_ptr = to_user_pointer(&batch),
> +			.buffer_count = 1,
> +			.rsvd1 = ctx,
> +		};
> +		unsigned int count;
> +		igt_spin_t *spin;
> +
> +		siblings = list_engines(i915, 1u << class, &count);
> +		if (!siblings)
> +			continue;
> +
> +		if (count < 2) {
> +			free(siblings);
> +			continue;
> +		}
> +
> +		/* A: spin forever on engine 1 */
> +		set_load_balancer(i915, ctx, siblings, count, NULL);
> +		spin = igt_spin_new(i915,
> +				    .ctx = ctx,
> +				    .engine = 1,
> +				    .flags = (IGT_SPIN_POLL_RUN |
> +					      IGT_SPIN_FENCE_OUT));
> +		igt_spin_busywait_until_started(spin);
> +
> +		/* B: waits for A on engine 2 */
> +		set_load_balancer(i915, ctx, siblings, count, NULL);
> +		execbuf.rsvd2 = spin->out_fence;
> +		execbuf.flags = I915_EXEC_FENCE_IN | I915_EXEC_FENCE_OUT;
> +		execbuf.flags |= 2; /* opposite engine to spinner */

Why or?

> +		gem_execbuf_wr(i915, &execbuf);
> +
> +		/* B': run in parallel with B on engine 1, i.e. not before A! */
> +		set_load_balancer(i915, ctx, siblings, count, NULL);

Why are you repeating the same set_load_balancer calls?

> +		execbuf.flags = I915_EXEC_FENCE_SUBMIT | I915_EXEC_FENCE_OUT;
> +		execbuf.flags |= 1; /* same engine as spinner */

Engine 3? But there are only two engines in the map, plus the virtual. 
So 0, 1, 2 - how does this work for you?

> +		execbuf.rsvd2 >>= 32;
> +		gem_execbuf_wr(i915, &execbuf);
> +
> +		/* Wait for any magic timeslicing or preemptions... */
> +		igt_assert_eq(sync_fence_wait(execbuf.rsvd2 >> 32, 1000),
> +			      -ETIME);
> +
> +		igt_debugfs_dump(i915, "i915_engine_info");
> +
> +		/*
> +		 * ... which should not have happened, so everything is still
> +		 * waiting on the spinner
> +		 */
> +		igt_assert_eq(sync_fence_status(spin->out_fence), 0);
> +		igt_assert_eq(sync_fence_status(execbuf.rsvd2 & 0xffffffff), 0);
> +		igt_assert_eq(sync_fence_status(execbuf.rsvd2 >> 32), 0);
> +
> +		igt_spin_free(i915, spin);
> +		gem_sync(i915, batch.handle);
> +
> +		igt_assert_eq(sync_fence_status(execbuf.rsvd2 & 0xffffffff), 1);
> +		igt_assert_eq(sync_fence_status(execbuf.rsvd2 >> 32), 1);
> +
> +		close(execbuf.rsvd2);
> +		close(execbuf.rsvd2 >> 32);
> +	}

How evil to lower ctx prio for A only?

> +
> +	gem_context_destroy(i915, ctx);
> +	gem_close(i915, batch.handle);
> +}
> +
>   static void indices(int i915)
>   {
>   	I915_DEFINE_CONTEXT_PARAM_ENGINES(engines, I915_EXEC_RING_MASK + 1);
> @@ -1580,6 +1665,9 @@ igt_main
>   	igt_subtest("bonded-slice")
>   		bonded_slice(i915);
>   
> +	igt_subtest("bonded-chain")
> +		bonded_chain(i915);
> +
>   	igt_fixture {
>   		igt_stop_hang_detector();
>   	}
> 

Regards,

Tvrtko
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