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

Chris Wilson
2019-11-01T10:11:48Z

Quoting Chris Wilson (2019-11-01 09:42:18)
> 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.

Other than that,
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>