Re: [PATCH 09/13] drm/i915: Add a tracepoint for using a semaphore

From: Daniel Vetter <daniel@ffwll.ch>
To: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
Cc: intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH 09/13] drm/i915: Add a tracepoint for using a semaphore
Date: Wed, 25 Sep 2013 12:11:12 +0200	[thread overview]
Message-ID: <20130925101112.GK12663@phenom.ffwll.local> (raw)
In-Reply-To: <20130925093437.GL4531@intel.com>

On Wed, Sep 25, 2013 at 12:34:37PM +0300, Ville Syrjälä wrote:
> On Mon, Sep 23, 2013 at 05:33:26PM -0300, Rodrigo Vivi wrote:
> > From: Chris Wilson <chris@chris-wilson.co.uk>
> > 
> > So that we can find the callers who introduce a ring stall. A single
> > ring stall is not too unwelcome, the right issue becomes when they start
> > to interlock and prevent any concurrent work. That, however, is a little
> > tricker to detect with a mere tracepoint!
> > 
> > v2: Rebrand it as a ring event, rather than an object event.
> > 
> > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> > Signed-off-by: Rodrigo Vivi <rodrigo.vivi@gmail.com>
> 
> Just wondering if we would want to see the seqno(s) in the trace as well?

Hm yeah, I guess the seqno we're syncing on the from ring would be useful
to gauge how much parallelism there really is. Chris, care to respin?
-Daniel

> 
> But anyway, the patch looks fine.
> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> > ---
> >  drivers/gpu/drm/i915/i915_gem.c   |  2 ++
> >  drivers/gpu/drm/i915/i915_trace.h | 19 +++++++++++++++++++
> >  2 files changed, 21 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> > index d68cc5c..4a16491 100644
> > --- a/drivers/gpu/drm/i915/i915_gem.c
> > +++ b/drivers/gpu/drm/i915/i915_gem.c
> > @@ -2614,6 +2614,8 @@ i915_gem_object_sync(struct drm_i915_gem_object *obj,
> >  	if (ret)
> >  		return ret;
> >  
> > +	trace_i915_gem_ring_sync_to(from, to);
> > +
> >  	ret = to->sync_to(to, from, seqno);
> >  	if (!ret)
> >  		/* We use last_read_seqno because sync_to()
> > diff --git a/drivers/gpu/drm/i915/i915_trace.h b/drivers/gpu/drm/i915/i915_trace.h
> > index 5c8e36a..48e8f07 100644
> > --- a/drivers/gpu/drm/i915/i915_trace.h
> > +++ b/drivers/gpu/drm/i915/i915_trace.h
> > @@ -233,6 +233,25 @@ TRACE_EVENT(i915_gem_evict_everything,
> >  	    TP_printk("dev=%d", __entry->dev)
> >  );
> >  
> > +TRACE_EVENT(i915_gem_ring_sync_to,
> > +	    TP_PROTO(struct intel_ring_buffer *from, struct intel_ring_buffer *to),
> > +	    TP_ARGS(from, to),
> > +
> > +	    TP_STRUCT__entry(
> > +			     __field(u32, dev)
> > +			     __field(u32, sync_from)
> > +			     __field(u32, sync_to)
> > +			     ),
> > +
> > +	    TP_fast_assign(
> > +			   __entry->dev = from->dev->primary->index;
> > +			   __entry->sync_from = from->id;
> > +			   __entry->sync_to = to->id;
> > +			   ),
> > +
> > +	    TP_printk("dev=%u, sync-from=%u, sync-to=%u", __entry->dev, __entry->sync_from, __entry->sync_to)
> > +);
> > +
> >  TRACE_EVENT(i915_gem_ring_dispatch,
> >  	    TP_PROTO(struct intel_ring_buffer *ring, u32 flags),
> >  	    TP_ARGS(ring, flags),
> > -- 
> > 1.8.1.4
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> -- 
> Ville Syrjälä
> Intel OTC
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch