Re: [RFC 4/8] drm/i915: Insert commands for capturing timestamps in the ring

["Gupta, Sourab" <sourab.gupta@intel.com>]

On Wed, 2015-08-05 at 09:30 +0000, Chris Wilson wrote:
> On Wed, Aug 05, 2015 at 11:25:40AM +0530, sourab.gupta@intel.com wrote:
> > From: Sourab Gupta <sourab.gupta@intel.com>
> > 
> > This patch adds the routines through which one can insert commands in the
> > ringbuf for capturing timestamps, which are used to insert these commands
> > around the batchbuffer.
> > 
> > While inserting the commands, we keep a reference of associated request.
> > This will be released when we are forwarding the samples to userspace
> > (or when the event is being destroyed).
> > Also, an active reference of the destination buffer is taken here, so that
> > we can be assured that the buffer is freed up only after GPU is done with
> > it, even if the local reference of the buffer is released.
> > 
> > v2: Changes (as suggested by Chris):
> >     - Passing in 'request' struct for emit report function
> >     - Removed multiple calls to i915_gem_obj_to_ggtt(). Keeping hold of
> >       pinned vma from start and using when required.
> >     - Better nomenclature, and error handling.
> > 
> > @@ -919,6 +993,7 @@ static int init_gen_pmu_buffer(struct perf_event *event)
> >  	dev_priv->gen_pmu.buffer.obj = bo;
> >  	dev_priv->gen_pmu.buffer.gtt_offset =
> >  				i915_gem_obj_ggtt_offset(bo);
> > +	dev_priv->gen_pmu.buffer.vma = i915_gem_obj_to_ggtt(bo);
> >  	dev_priv->gen_pmu.buffer.addr = vmap_oa_buffer(bo);
> >  	INIT_LIST_HEAD(&dev_priv->gen_pmu.node_list);
> 
> Still calling i915_gem_obj_to_ggtt(bo) twice! With pmu_buffer.vma you
> can drop pmu_buffer.gtt_offset and never be confused again.
> -Chris
> 
Sorry, I'll have the one pertaining to gtt offset removed, and derive
the gtt offset field from the vma only.


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