[Intel-gfx] [PATCH v2 1/4] drm/i915: Get active pending request for given context

[Navik, Ankit P]

Hi Tvrtko, 

> On Tue, Nov 6, 2018 at 3:14 PM Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com> wrote:
> 
> 
> On 06/11/2018 04:13, Ankit Navik wrote:
> > From: Praveen Diwakar <praveen.diwakar at intel.com>
> >
> > This patch gives us the active pending request count which is yet to
> > be submitted to the GPU
> >
> > Signed-off-by: Praveen Diwakar <praveen.diwakar at intel.com>
> > Signed-off-by: Yogesh Marathe <yogesh.marathe at intel.com>
> > Signed-off-by: Aravindan Muthukumar <aravindan.muthukumar at intel.com>
> > Signed-off-by: Kedar J Karanje <kedar.j.karanje at intel.com>
> > Signed-off-by: Ankit Navik <ankit.p.navik at intel.com>
> > Suggested-by: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
> > ---
> >   drivers/gpu/drm/i915/i915_drv.c            | 1 +
> >   drivers/gpu/drm/i915/i915_drv.h            | 5 +++++
> >   drivers/gpu/drm/i915/i915_gem_context.c    | 1 +
> >   drivers/gpu/drm/i915/i915_gem_context.h    | 6 ++++++
> >   drivers/gpu/drm/i915/i915_gem_execbuffer.c | 5 +++++
> >   drivers/gpu/drm/i915/intel_lrc.c           | 6 ++++++
> >   6 files changed, 24 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_drv.c
> > b/drivers/gpu/drm/i915/i915_drv.c index f8cfd16..d37c46e 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.c
> > +++ b/drivers/gpu/drm/i915/i915_drv.c
> > @@ -903,6 +903,7 @@ static int i915_driver_init_early(struct
> drm_i915_private *dev_priv,
> >   	mutex_init(&dev_priv->av_mutex);
> >   	mutex_init(&dev_priv->wm.wm_mutex);
> >   	mutex_init(&dev_priv->pps_mutex);
> > +	mutex_init(&dev_priv->pred_mutex);
> >
> >   	i915_memcpy_init_early(dev_priv);
> >
> > diff --git a/drivers/gpu/drm/i915/i915_drv.h
> > b/drivers/gpu/drm/i915/i915_drv.h index 4aca534..137ec33 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.h
> > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > @@ -1609,6 +1609,11 @@ struct drm_i915_private {
> >   	 * controller on different i2c buses. */
> >   	struct mutex gmbus_mutex;
> >
> > +	/** pred_mutex protects against councurrent usage of pending
> > +	 * request counter for multiple contexts
> > +	 */
> > +	struct mutex pred_mutex;
> > +
> >   	/**
> >   	 * Base address of the gmbus and gpio block.
> >   	 */
> > diff --git a/drivers/gpu/drm/i915/i915_gem_context.c
> > b/drivers/gpu/drm/i915/i915_gem_context.c
> > index b10770c..0bcbe32 100644
> > --- a/drivers/gpu/drm/i915/i915_gem_context.c
> > +++ b/drivers/gpu/drm/i915/i915_gem_context.c
> > @@ -387,6 +387,7 @@ i915_gem_create_context(struct drm_i915_private
> *dev_priv,
> >   	}
> >
> >   	trace_i915_context_create(ctx);
> > +	atomic_set(&ctx->req_cnt, 0);
> >
> >   	return ctx;
> >   }
> > diff --git a/drivers/gpu/drm/i915/i915_gem_context.h
> > b/drivers/gpu/drm/i915/i915_gem_context.h
> > index b116e49..04e3ff7 100644
> > --- a/drivers/gpu/drm/i915/i915_gem_context.h
> > +++ b/drivers/gpu/drm/i915/i915_gem_context.h
> > @@ -194,6 +194,12 @@ struct i915_gem_context {
> >   	 * context close.
> >   	 */
> >   	struct list_head handles_list;
> > +
> > +	/** req_cnt: tracks the pending commands, based on which we decide
> to
> > +	 * go for low/medium/high load configuration of the GPU, this is
> > +	 * controlled via a mutex
> > +	 */
> > +	atomic_t req_cnt;
> >   };
> >
> >   static inline bool i915_gem_context_is_closed(const struct
> > i915_gem_context *ctx) diff --git
> > a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> > b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> > index 3f0c612..8afa2a5 100644
> > --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> > +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> > @@ -2178,6 +2178,7 @@ i915_gem_do_execbuffer(struct drm_device *dev,
> >   		       struct drm_syncobj **fences)
> >   {
> >   	struct i915_execbuffer eb;
> > +	struct drm_i915_private *dev_priv = to_i915(dev);
> >   	struct dma_fence *in_fence = NULL;
> >   	struct sync_file *out_fence = NULL;
> >   	int out_fence_fd = -1;
> > @@ -2390,6 +2391,10 @@ i915_gem_do_execbuffer(struct drm_device *dev,
> >   	 */
> >   	eb.request->batch = eb.batch;
> >
> > +	mutex_lock(&dev_priv->pred_mutex);
> > +	atomic_inc(&eb.ctx->req_cnt);
> 
> Point of going to atomic_t was to remove need for the mutex.
> 
> > +	mutex_unlock(&dev_priv->pred_mutex);
> > +
> >   	trace_i915_request_queue(eb.request, eb.batch_flags);
> >   	err = eb_submit(&eb);
> >   err_request:
> > diff --git a/drivers/gpu/drm/i915/intel_lrc.c
> > b/drivers/gpu/drm/i915/intel_lrc.c
> > index 1744792..bcbb66b 100644
> > --- a/drivers/gpu/drm/i915/intel_lrc.c
> > +++ b/drivers/gpu/drm/i915/intel_lrc.c
> > @@ -728,6 +728,12 @@ static void execlists_dequeue(struct intel_engine_cs
> *engine)
> >   			trace_i915_request_in(rq, port_index(port, execlists));
> >   			last = rq;
> >   			submit = true;
> > +
> > +			mutex_lock(&rq->i915->pred_mutex);
> > +			if (atomic_read(&rq->gem_context->req_cnt) > 0)
> > +				atomic_dec(&rq->gem_context->req_cnt);
> 
> Hitting underflow is a hint accounting does not work as expected. I really think
> you need to fix it by gathering some ideas from the patches I've pointed at in the
> previous round.

Changes submitted in v3 patch.
https://patchwork.freedesktop.org/patch/267386/ 

Regards, 
Ankit
> 
> And there is also GuC to think about.
> 
> Regards,
> 
> Tvrtko
> 
> > +
> > +			mutex_unlock(&rq->i915->pred_mutex);
> >   		}
> >
> >   		rb_erase_cached(&p->node, &execlists->queue);
> >