Re: [Intel-gfx] [PATCH] drm/i915/gem: Use large rings for compute contexts

[Jani Nikula <jani.nikula@linux.intel.com>]

On Tue, 16 May 2023, Tejas Upadhyay <tejas.upadhyay@intel.com> wrote:
> From: Chris Wilson <chris.p.wilson@intel.com>
>
> Allow compute contexts to submit the maximal amount of work without
> blocking userspace.
>
> The original size for user LRC ring's (SZ_16K) was chosen to minimise
> memory consumption, without being so small as to frequently stall in the
> middle of workloads. With the main consumers being GL / media pipelines
> of 2 or 3 batches per frame, we want to support ~10 requests in flight
> to allow for the application to control throttling without stalling
> within a frame.
>
> Signed-off-by: Chris Wilson <chris.p.wilson@intel.com>
> ---
>  drivers/gpu/drm/i915/gem/i915_gem_context.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> index 5402a7bbcb1d..0edb7be6fa5e 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> @@ -965,6 +965,8 @@ static int intel_context_set_gem(struct intel_context *ce,
>  
>  	GEM_BUG_ON(intel_context_is_pinned(ce));
>  	ce->ring_size = SZ_16K;
> +	if (ce->engine->class == COMPUTE_CLASS)
> +		ce->ring_size = SZ_512K;

Not a huge fan of first initializing something, and then changing it in
some cases.

Why not if (ce->engine->class == COMPUTE_CLASS) ... else ...?

BR,
Jani.


>  
>  	i915_vm_put(ce->vm);
>  	ce->vm = i915_gem_context_get_eb_vm(ctx);

-- 
Jani Nikula, Intel Open Source Graphics Center