[Intel-gfx] [PATCH 05/10] drm/i915: Track runtime spent in unreachable intel_contexts

[Chris Wilson]

Quoting Tvrtko Ursulin (2020-03-18 12:11:34)
> From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> 
> As contexts are abandoned we want to remember how much GPU time they used
> (per class) so later we can used it for smarter purposes.
> 
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> ---
>  drivers/gpu/drm/i915/gem/i915_gem_context.c       | 13 ++++++++++++-
>  drivers/gpu/drm/i915/gem/i915_gem_context_types.h |  5 +++++
>  2 files changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> index 7c119a3a2cbd..5edf79ed6247 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> @@ -257,7 +257,19 @@ static void free_engines_rcu(struct rcu_head *rcu)
>  {
>         struct i915_gem_engines *engines =
>                 container_of(rcu, struct i915_gem_engines, rcu);
> +       struct i915_gem_context *ctx = engines->ctx;
> +       struct i915_gem_engines_iter it;
> +       struct intel_context *ce;
> +
> +       /* Transfer accumulated runtime to the parent GEM context. */
> +       for_each_gem_engine(ce, engines, it) {
> +               unsigned int class = ce->engine->uabi_class;
>  
> +               GEM_BUG_ON(class >= ARRAY_SIZE(ctx->past_runtime));
> +               atomic64_add(ce->runtime.total, &ctx->past_runtime[class]);

Hmm, there's an odd situation where the free_engines_rcu could fire
before we do the final schedule_out of the context.

GEM_BUG_ON(intel_context_inflight(ce)) to see if that's being too
paranoid.
-Chris