Re: [Intel-gfx] [RFC PATCH i-g-t v4 4/4] tests/gem_ctx_shared: Align objects using minimum GTT alignment

Chris Wilson
2019-11-01T09:42:18Z

Quoting Janusz Krzysztofik (2019-10-31 15:28:57)
> exec-shared-gtt-* subtests use hardcoded values for object size and
> softpin offset, based on 4kB GTT alignment assumption. That may result
> in those subtests failing when run on future backing stores with
> possibly larger minimum page sizes.
>
> Replace hardcoded constants with values calculated from minimum GTT
> alignment of actual backing store the test is running on.
>
> v2: Update helper name, use 'minimum GTT alignment' term across the
> change, adjust variable name.
>
> Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> ---
> tests/i915/gem_ctx_shared.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/tests/i915/gem_ctx_shared.c b/tests/i915/gem_ctx_shared.c
> index 6d8cbcce..1e9c7f78 100644
> --- a/tests/i915/gem_ctx_shared.c
> +++ b/tests/i915/gem_ctx_shared.c
> @@ -195,6 +195,7 @@ static void exec_shared_gtt(int i915, unsigned int ring)
> uint32_t scratch, *s;
> uint32_t batch, cs[16];
> uint64_t offset;
> + uint64_t alignment;
> int i;
>
> gem_require_ring(i915, ring);
> @@ -203,7 +204,8 @@ static void exec_shared_gtt(int i915, unsigned int ring)
> clone = gem_context_clone(i915, 0, I915_CONTEXT_CLONE_VM, 0);
>
> /* Find a hole big enough for both objects later */
> - scratch = gem_create(i915, 16384);
> + alignment = 2 * gem_gtt_min_alignment(i915);
> + scratch = gem_create(i915, 2 * alignment);
> gem_write(i915, scratch, 0, &bbe, sizeof(bbe));
> obj.handle = scratch;
> gem_execbuf(i915, &execbuf);
> @@ -246,7 +248,7 @@ static void exec_shared_gtt(int i915, unsigned int ring)
> gem_write(i915, batch, 0, cs, sizeof(cs));
>
> obj.handle = batch;
> - obj.offset += 8192; /* make sure we don't cause an eviction! */
> + obj.offset += alignment; /* make sure we don't cause an eviction! */

It's 'stride' here. It's leaving a guard page in between, just in case
page coloring demands it.
-Chris
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