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

[Tvrtko Ursulin]

On 18/03/2020 13:55, Chris Wilson wrote:
> 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.

Deja vu.. have I forgotten to move this into intel_context_free while 
the purpose of keeping ce->gem_context valid was exactly to enable that.

Regards,

Tvrtko