[Intel-gfx] [PATCH 1/6] drm/i915: Extend i915 perf framework for collecting timestamps on all gpu engines

[sourab gupta]

On Thu, 2017-03-16 at 00:49 -0700, Chris Wilson wrote:
> On Thu, Mar 16, 2017 at 11:50:06AM +0530, sourab.gupta at intel.com wrote:
> > From: Sourab Gupta <sourab.gupta at intel.com>
> > 
> > This patch extends the i915  perf framework to handle the perf sample
> > collection for any given gpu engine. Particularly, the support
> > for collecting timestamp sample type is added, which can be requested for
> > any engine.
> > With this, for RCS, timestamps and OA reports can be collected together,
> > and provided to userspace in separate sample fields. For other engines,
> > the capabilility to collect timestamps is added.
> > 
> > The thing to note is that, still only a single stream instance can be
> > opened at any particular time. Though that stream may now be opened for any
> > gpu engine, for collection of timestamp samples.
> > 
> > So, this patch doesn't add the support to open multiple concurrent streams,
> > as yet. Though it lays the groundwork for this support to be added
> > susequently. Part of this groundwork involves having separate command
> > stream buffers, per engine, for holding the samples generated.
> > Likewise for a few other data structures maintaining per-engine state.
> > 
> > Signed-off-by: Sourab Gupta <sourab.gupta at intel.com>
> > ---
> > @@ -2519,15 +2546,14 @@ struct drm_i915_private {
> >  
> >  		spinlock_t hook_lock;
> >  
> > -		struct {
> > -			struct i915_perf_stream *exclusive_stream;
> > +		struct hrtimer poll_check_timer;
> > +		struct i915_perf_stream *exclusive_stream;
> > +		wait_queue_head_t poll_wq[I915_NUM_ENGINES];
> > +		bool pollin[I915_NUM_ENGINES];
> 
> So what's the rationale for not storing these [NUM_ENGINES] on the
> engines?
> -Chris
> 
I wanted to keep the perf related stuff clubbed together under
dev_priv->perf, and not distribute this stuff over intel_engine_cs.
Thus, the design choice of having [NUM_ENGINES] instances of these
fields.
Does this seem okay?

Regards,
Sourab