[Intel-gfx] [PATCH 3/6] drm/i915: Only track live rings for retiring
Tvrtko Ursulin
tvrtko.ursulin at linux.intel.com
Mon Apr 23 10:50:26 UTC 2018
On 23/04/2018 11:36, Chris Wilson wrote:
> Quoting Tvrtko Ursulin (2018-04-23 11:25:54)
>>
>> On 23/04/2018 11:13, Chris Wilson wrote:
>>> We don't need to track every ring for its lifetime as they are managed
>>> by the contexts/engines. What we do want to track are the live rings so
>>> that we can sporadically clean up requests if userspace falls behind. We
>>> can simply restrict the gt->rings list to being only gt->live_rings.
>>>
>>> Suggested-by: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
>>> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
>>> Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
>>> ---
>>> drivers/gpu/drm/i915/i915_drv.h | 2 +-
>>> drivers/gpu/drm/i915/i915_gem.c | 3 ++-
>>> drivers/gpu/drm/i915/i915_request.c | 6 +++++-
>>> drivers/gpu/drm/i915/i915_utils.h | 6 ++++++
>>> drivers/gpu/drm/i915/intel_ringbuffer.c | 4 ----
>>> drivers/gpu/drm/i915/intel_ringbuffer.h | 2 +-
>>> drivers/gpu/drm/i915/selftests/mock_engine.c | 4 ----
>>> drivers/gpu/drm/i915/selftests/mock_gem_device.c | 2 +-
>>> 8 files changed, 16 insertions(+), 13 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
>>> index 73936be90aed..a7787c2cb53c 100644
>>> --- a/drivers/gpu/drm/i915/i915_drv.h
>>> +++ b/drivers/gpu/drm/i915/i915_drv.h
>>> @@ -2060,7 +2060,7 @@ struct drm_i915_private {
>>>
>>> struct i915_gem_timeline global_timeline;
>>> struct list_head timelines;
>>> - struct list_head rings;
>>> + struct list_head live_rings;
>>> u32 active_requests;
>>>
>>> /**
>>> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
>>> index 906e2395c245..0097a77fae8d 100644
>>> --- a/drivers/gpu/drm/i915/i915_gem.c
>>> +++ b/drivers/gpu/drm/i915/i915_gem.c
>>> @@ -141,6 +141,7 @@ static u32 __i915_gem_park(struct drm_i915_private *i915)
>>> {
>>> lockdep_assert_held(&i915->drm.struct_mutex);
>>> GEM_BUG_ON(i915->gt.active_requests);
>>> + GEM_BUG_ON(!list_empty(&i915->gt.live_rings));
>>>
>>> if (!i915->gt.awake)
>>> return I915_EPOCH_INVALID;
>>> @@ -5600,7 +5601,7 @@ int i915_gem_init_early(struct drm_i915_private *dev_priv)
>>> goto err_dependencies;
>>>
>>> mutex_lock(&dev_priv->drm.struct_mutex);
>>> - INIT_LIST_HEAD(&dev_priv->gt.rings);
>>> + INIT_LIST_HEAD(&dev_priv->gt.live_rings);
>>> INIT_LIST_HEAD(&dev_priv->gt.timelines);
>>> err = i915_gem_timeline_init__global(dev_priv);
>>> mutex_unlock(&dev_priv->drm.struct_mutex);
>>> diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
>>> index 0bf949ec9f1a..534b8d684cef 100644
>>> --- a/drivers/gpu/drm/i915/i915_request.c
>>> +++ b/drivers/gpu/drm/i915/i915_request.c
>>> @@ -316,6 +316,7 @@ static void advance_ring(struct i915_request *request)
>>> * noops - they are safe to be replayed on a reset.
>>> */
>>> tail = READ_ONCE(request->tail);
>>> + list_del(&ring->live);
>>> } else {
>>> tail = request->postfix;
>>> }
>>> @@ -1046,6 +1047,8 @@ void __i915_request_add(struct i915_request *request, bool flush_caches)
>>> i915_gem_active_set(&timeline->last_request, request);
>>>
>>> list_add_tail(&request->ring_link, &ring->request_list);
>>> + if (list_is_first(&request->ring_link, &ring->request_list))
>>> + list_add(&ring->live, &request->i915->gt.live_rings);
>>
>> If you re-order the two list adds you could use list_empty and wouldn't
>> have to add list_is_first.
>
> list_is_first tallies nicely with the list_is_last used before the
> corresponding list_del.
Yes but to me that's minor, basically immaterial as argument whether or
not to add our own list helper.
>>
>>> request->emitted_jiffies = jiffies;
>>>
>>> /*
>>> @@ -1375,7 +1378,8 @@ void i915_retire_requests(struct drm_i915_private *i915)
>>> if (!i915->gt.active_requests)
>>> return;
>>>
>>> - list_for_each_entry_safe(ring, next, &i915->gt.rings, link)
>>> + GEM_BUG_ON(list_empty(&i915->gt.live_rings));
>>
>> Maybe blank line here since the assert is not logically associated with
>> the list but with the !i915.active_requests?
>
> I was thinking list when I wrote it. It's small enough we can argue both
> and both be right.
Hm obviosuly it is not an error to call i915_retire_requests with
nothing active (early return). So I even briefly wanted to suggest to
make it 100% explicit and have the assert at the top of the function as:
GEM_BUG_ON(!!i915->gt.active_requests ^ !!list_empty(..));
Unless I messed it up, the idea is to check those two are always in the
same state.
>
>>
>>> + list_for_each_entry_safe(ring, next, &i915->gt.live_rings, live)
>>> ring_retire_requests(ring);
>>> }
>>>
>>> diff --git a/drivers/gpu/drm/i915/i915_utils.h b/drivers/gpu/drm/i915/i915_utils.h
>>> index 0695717522ea..00165ad55fb3 100644
>>> --- a/drivers/gpu/drm/i915/i915_utils.h
>>> +++ b/drivers/gpu/drm/i915/i915_utils.h
>>> @@ -120,6 +120,12 @@ static inline u64 ptr_to_u64(const void *ptr)
>>>
>>> #include <linux/list.h>
>>>
>>> +static inline int list_is_first(const struct list_head *list,
>>> + const struct list_head *head)
>>
>> Return bool if you decide you prefer to keep list_is_first?
>
> Copy'n'paste from list_is_last().
>
>>
>>> +{
>>> + return head->next == list;
>>> +}
>>> +
>>> static inline void __list_del_many(struct list_head *head,
>>> struct list_head *first)
>>> {
>>> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
>>> index 792a2ca95872..3453e7426f6b 100644
>>> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
>>> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
>>> @@ -1150,8 +1150,6 @@ intel_engine_create_ring(struct intel_engine_cs *engine, int size)
>>> }
>>> ring->vma = vma;
>>>
>>> - list_add(&ring->link, &engine->i915->gt.rings);
>>> -
>>> return ring;
>>> }
>>>
>>> @@ -1163,8 +1161,6 @@ intel_ring_free(struct intel_ring *ring)
>>> i915_vma_close(ring->vma);
>>> __i915_gem_object_release_unless_active(obj);
>>>
>>> - list_del(&ring->link);
>>> -
>>> kfree(ring);
>>> }
>>>
>>> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
>>> index d816f8dea245..fd5a6363ab1d 100644
>>> --- a/drivers/gpu/drm/i915/intel_ringbuffer.h
>>> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
>>> @@ -129,7 +129,7 @@ struct intel_ring {
>>> void *vaddr;
>>>
>>> struct list_head request_list;
>>> - struct list_head link;
>>> + struct list_head live;
>>
>> live_link?
>
> live or active.
>
> active_rings ties in with active_requests, so active_link here.
Fine by me.
Regards,
Tvrtko
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