Re: [PATCH] drm/i915/pmu: Atomically acquire the gt_pm wakeref

[Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>]

On 01/08/2019 15:39, Chris Wilson wrote:
> Quoting Tvrtko Ursulin (2019-08-01 15:21:17)
> > On 01/08/2019 13:20, Chris Wilson wrote:
> > > Currently, we only sample if the intel_gt is awake, but we acquire our
> > > own runtime_pm wakeref. Since intel_gt has transitioned to tracking its
> > > own wakeref, we can atomically test and acquire that wakeref instead.
> > >
> > > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > > Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> > > ---
> > > No automagic drop!
> > > ---
> > >    drivers/gpu/drm/i915/gt/intel_gt_pm.h |  8 +++++++-
> > >    drivers/gpu/drm/i915/i915_pmu.c       | 23 ++++++++---------------
> > >    2 files changed, 15 insertions(+), 16 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/gt/intel_gt_pm.h b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
> > > index ba960e1fc209..016298483de7 100644
> > > --- a/drivers/gpu/drm/i915/gt/intel_gt_pm.h
> > > +++ b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
> > > @@ -9,7 +9,8 @@
> > >    
> > >    #include <linux/types.h>
> > >    
> > > -struct intel_gt;
> > > +#include "intel_gt_types.h"
> > > +#include "intel_wakeref.h"
> > >    
> > >    enum {
> > >        INTEL_GT_UNPARK,
> > > @@ -19,6 +20,11 @@ enum {
> > >    void intel_gt_pm_get(struct intel_gt *gt);
> > >    void intel_gt_pm_put(struct intel_gt *gt);
> > >    
> > > +static inline bool intel_gt_pm_get_if_awake(struct intel_gt *gt)
> > > +{
> > > +     return intel_wakeref_get_if_active(&gt->wakeref);
> > > +}
> > > +
> > >    void intel_gt_pm_init_early(struct intel_gt *gt);
> > >    
> > >    void intel_gt_sanitize(struct intel_gt *gt, bool force);
> > > diff --git a/drivers/gpu/drm/i915/i915_pmu.c b/drivers/gpu/drm/i915/i915_pmu.c
> > > index eff86483bec0..e71192804996 100644
> > > --- a/drivers/gpu/drm/i915/i915_pmu.c
> > > +++ b/drivers/gpu/drm/i915/i915_pmu.c
> > > @@ -8,6 +8,7 @@
> > >    #include <linux/pm_runtime.h>
> > >    
> > >    #include "gt/intel_engine.h"
> > > +#include "gt/intel_gt_pm.h"
> > >    
> > >    #include "i915_drv.h"
> > >    #include "i915_pmu.h"
> > > @@ -161,16 +162,12 @@ engines_sample(struct drm_i915_private *dev_priv, unsigned int period_ns)
> > >    {
> > >        struct intel_engine_cs *engine;
> > >        enum intel_engine_id id;
> > > -     intel_wakeref_t wakeref;
> > >        unsigned long flags;
> > >    
> > >        if ((dev_priv->pmu.enable & ENGINE_SAMPLE_MASK) == 0)
> > >                return;
> > >    
> > > -     wakeref = 0;
> > > -     if (READ_ONCE(dev_priv->gt.awake))
> > > -             wakeref = intel_runtime_pm_get_if_in_use(&dev_priv->runtime_pm);
> > > -     if (!wakeref)
> > > +     if (!intel_gt_pm_get_if_awake(&dev_priv->gt))
> > >                return;
> > >    
> > >        spin_lock_irqsave(&dev_priv->uncore.lock, flags);
> > > @@ -205,7 +202,7 @@ engines_sample(struct drm_i915_private *dev_priv, unsigned int period_ns)
> > >        }
> > >        spin_unlock_irqrestore(&dev_priv->uncore.lock, flags);
> > >    
> > > -     intel_runtime_pm_put(&dev_priv->runtime_pm, wakeref);
> > > +     intel_gt_pm_put(&dev_priv->gt);
> > >    }
> > >    
> > >    static void
> > > @@ -222,15 +219,11 @@ frequency_sample(struct drm_i915_private *dev_priv, unsigned int period_ns)
> > >                u32 val;
> > >    
> > >                val = dev_priv->gt_pm.rps.cur_freq;
> > > -             if (dev_priv->gt.awake) {
> > > -                     intel_wakeref_t wakeref;
> > > -
> > > -                     with_intel_runtime_pm_if_in_use(&dev_priv->runtime_pm,
> > > -                                                     wakeref) {
> > > -                             val = intel_uncore_read_notrace(&dev_priv->uncore,
> > > -                                                             GEN6_RPSTAT1);
> > > -                             val = intel_get_cagf(dev_priv, val);
> > > -                     }
> > > +             if (intel_gt_pm_get_if_awake(&dev_priv->gt)) {
> > > +                     val = intel_uncore_read_notrace(&dev_priv->uncore,
> > > +                                                     GEN6_RPSTAT1);
> > > +                     val = intel_get_cagf(dev_priv, val);
> > > +                     intel_gt_pm_put(&dev_priv->gt);
> > >                }
> > >    
> > >                add_sample_mult(&dev_priv->pmu.sample[__I915_SAMPLE_FREQ_ACT],
> >
> > I guess I'll be rebasing mine, at some point. :)
>
> I anticipated you merging it at some point.

This patch to my series or what?

> Had a thought, and we don't need gt_pm for the engine sampling, but
> rather intel_engine_pm_get_if_awake.

I thought about it, but since we iterate all engines did not see a real 
benefit. Wouldn't harm either, only some more CPU cycles in the loop, so 
up to you.

Regards,

Tvrtko
_______________________________________________
Intel-gfx mailing list
Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/intel-gfx