Re: [PATCH 2/2] drm/i915/pmu: Make PMU sample array two-dimensional

[Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>]

On 24/05/2023 18:38, Dixit, Ashutosh wrote:
> On Wed, 24 May 2023 04:38:18 -0700, Tvrtko Ursulin wrote:
> >
>
> Hi Tvrtko,
>
> > On 23/05/2023 16:19, Ashutosh Dixit wrote:
> > > No functional changes but we can remove some unsightly index computation
> > > and read/write functions if we convert the PMU sample array from a
> > > one-dimensional to a two-dimensional array.
> > >
> > > Suggested-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>
> > > Signed-off-by: Ashutosh Dixit <ashutosh.dixit@xxxxxxxxx>
> > > ---
> > >    drivers/gpu/drm/i915/i915_pmu.c | 60 ++++++++++-----------------------
> > >    drivers/gpu/drm/i915/i915_pmu.h |  2 +-
> > >    2 files changed, 19 insertions(+), 43 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/i915_pmu.c b/drivers/gpu/drm/i915/i915_pmu.c
> > > index b47d890d4ada1..137e0df9573ee 100644
> > > --- a/drivers/gpu/drm/i915/i915_pmu.c
> > > +++ b/drivers/gpu/drm/i915/i915_pmu.c
> > > @@ -195,33 +195,6 @@ static inline s64 ktime_since_raw(const ktime_t kt)
> > > 	return ktime_to_ns(ktime_sub(ktime_get_raw(), kt));
> > >    }
> > >    -static unsigned int
> > > -__sample_idx(struct i915_pmu *pmu, unsigned int gt_id, int sample)
> > > -{
> > > -	unsigned int idx = gt_id * __I915_NUM_PMU_SAMPLERS + sample;
> > > -
> > > -	GEM_BUG_ON(idx >= ARRAY_SIZE(pmu->sample));
> > > -
> > > -	return idx;
> > > -}
> > > -
> > > -static u64 read_sample(struct i915_pmu *pmu, unsigned int gt_id, int sample)
> > > -{
> > > -	return pmu->sample[__sample_idx(pmu, gt_id, sample)].cur;
> > > -}
> > > -
> > > -static void
> > > -store_sample(struct i915_pmu *pmu, unsigned int gt_id, int sample, u64 val)
> > > -{
> > > -	pmu->sample[__sample_idx(pmu, gt_id, sample)].cur = val;
> > > -}
> > > -
> > > -static void
> > > -add_sample_mult(struct i915_pmu *pmu, unsigned int gt_id, int sample, u32 val, u32 mul)
> > > -{
> > > -	pmu->sample[__sample_idx(pmu, gt_id, sample)].cur += mul_u32_u32(val, mul);
> > > -}
> >
> > IMO read and store helpers could have stayed and just changed the
> > implementation. Like add_sample_mult which you just moved. I would have
> > been a smaller patch. So dunno.. a bit of a reluctant r-b.
>
> Are you referring just to add_sample_mult or to all the other functions
> too? add_sample_mult I moved it to where it was before bc4be0a38b63

Read and store helpers.

> ("drm/i915/pmu: Prepare for multi-tile non-engine counters"), could have
> left it here I guess.
>
> The other read and store helpers are not needed with the 2-d array at all
> since the compiler itself will do that, so I thought it was better to get
> rid of them completely.

Yes I get it, just that I didn't see the benefit of removing them.

For example:

 -		store_sample(pmu, gt_id, __I915_SAMPLE_RC6, val);
 +		pmu->sample[gt_id][__I915_SAMPLE_RC6].cur = val;

It's a meh for me. Either flavour looks fine to me so I would have erred 
on the side of keeping the patch small. If anything I probably slightly 
prefer that the struct pmu_sample implementation was able to be changed 
with less churn before. For example. But a very minor argument really.

Or maybe next step is get rid of the struct i915_pmu_sample. It is a 
struct because originally previous value was tracked too. Then I removed 
that and it was easier to keep the struct. I guess it can go now and 
then the removal of helpers here will look somewhat nicer without the 
trailing .cur on every affected line.

> Let me know if you want any changes, otherwise I will leave as is.

You can leave it as is, I dont' mind much.

Regards,

Tvrtko

> > Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
>
> Thanks for the review. Thanks Andrzej too :)
> --
> Ashutosh
>
> > > -
> > >    static u64 get_rc6(struct intel_gt *gt)
> > >    {
> > > 	struct drm_i915_private *i915 = gt->i915;
> > > @@ -240,7 +213,7 @@ static u64 get_rc6(struct intel_gt *gt)
> > > 	spin_lock_irqsave(&pmu->lock, flags);
> > > 		if (awake) {
> > > -		store_sample(pmu, gt_id, __I915_SAMPLE_RC6, val);
> > > +		pmu->sample[gt_id][__I915_SAMPLE_RC6].cur = val;
> > > 	} else {
> > > 		/*
> > > 		 * We think we are runtime suspended.
> > > @@ -250,13 +223,13 @@ static u64 get_rc6(struct intel_gt *gt)
> > > 		 * counter value.
> > > 		 */
> > > 		val = ktime_since_raw(pmu->sleep_last[gt_id]);
> > > -		val += read_sample(pmu, gt_id, __I915_SAMPLE_RC6);
> > > +		val += pmu->sample[gt_id][__I915_SAMPLE_RC6].cur;
> > > 	}
> > >    -	if (val < read_sample(pmu, gt_id, __I915_SAMPLE_RC6_LAST_REPORTED))
> > > -		val = read_sample(pmu, gt_id, __I915_SAMPLE_RC6_LAST_REPORTED);
> > > +	if (val < pmu->sample[gt_id][__I915_SAMPLE_RC6_LAST_REPORTED].cur)
> > > +		val = pmu->sample[gt_id][__I915_SAMPLE_RC6_LAST_REPORTED].cur;
> > > 	else
> > > -		store_sample(pmu, gt_id, __I915_SAMPLE_RC6_LAST_REPORTED, val);
> > > +		pmu->sample[gt_id][__I915_SAMPLE_RC6_LAST_REPORTED].cur = val;
> > > 		spin_unlock_irqrestore(&pmu->lock, flags);
> > >    @@ -275,9 +248,8 @@ static void init_rc6(struct i915_pmu *pmu)
> > > 		with_intel_runtime_pm(gt->uncore->rpm, wakeref) {
> > > 			u64 val = __get_rc6(gt);
> > >    -			store_sample(pmu, i, __I915_SAMPLE_RC6, val);
> > > -			store_sample(pmu, i, __I915_SAMPLE_RC6_LAST_REPORTED,
> > > -				     val);
> > > +			pmu->sample[i][__I915_SAMPLE_RC6].cur = val;
> > > +			pmu->sample[i][__I915_SAMPLE_RC6_LAST_REPORTED].cur = val;
> > > 			pmu->sleep_last[i] = ktime_get_raw();
> > > 		}
> > > 	}
> > > @@ -287,7 +259,7 @@ static void park_rc6(struct intel_gt *gt)
> > >    {
> > > 	struct i915_pmu *pmu = &gt->i915->pmu;
> > >    -	store_sample(pmu, gt->info.id, __I915_SAMPLE_RC6, __get_rc6(gt));
> > > +	pmu->sample[gt->info.id][__I915_SAMPLE_RC6].cur = __get_rc6(gt);
> > > 	pmu->sleep_last[gt->info.id] = ktime_get_raw();
> > >    }
> > >    @@ -428,6 +400,12 @@ engines_sample(struct intel_gt *gt, unsigned int
> > > period_ns)
> > > 	}
> > >    }
> > >    +static void
> > > +add_sample_mult(struct i915_pmu_sample *sample, u32 val, u32 mul)
> > > +{
> > > +	sample->cur += mul_u32_u32(val, mul);
> > > +}
> > > +
> > >    static bool
> > >    frequency_sampling_enabled(struct i915_pmu *pmu, unsigned int gt)
> > >    {
> > > @@ -467,12 +445,12 @@ frequency_sample(struct intel_gt *gt, unsigned int period_ns)
> > > 		if (!val)
> > > 			val = intel_gpu_freq(rps, rps->cur_freq);
> > >    -		add_sample_mult(pmu, gt_id, __I915_SAMPLE_FREQ_ACT,
> > > +		add_sample_mult(&pmu->sample[gt_id][__I915_SAMPLE_FREQ_ACT],
> > > 				val, period_ns / 1000);
> > > 	}
> > > 		if (pmu->enable &
> > > config_mask(__I915_PMU_REQUESTED_FREQUENCY(gt_id))) {
> > > -		add_sample_mult(pmu, gt_id, __I915_SAMPLE_FREQ_REQ,
> > > +		add_sample_mult(&pmu->sample[gt_id][__I915_SAMPLE_FREQ_REQ],
> > > 				intel_rps_get_requested_frequency(rps),
> > > 				period_ns / 1000);
> > > 	}
> > > @@ -673,14 +651,12 @@ static u64 __i915_pmu_event_read(struct perf_event *event)
> > > 		switch (config) {
> > > 		case I915_PMU_ACTUAL_FREQUENCY:
> > > 			val =
> > > -			   div_u64(read_sample(pmu, gt_id,
> > > -					       __I915_SAMPLE_FREQ_ACT),
> > > +			   div_u64(pmu->sample[gt_id][__I915_SAMPLE_FREQ_ACT].cur,
> > > 				   USEC_PER_SEC /* to MHz */);
> > > 			break;
> > > 		case I915_PMU_REQUESTED_FREQUENCY:
> > > 			val =
> > > -			   div_u64(read_sample(pmu, gt_id,
> > > -					       __I915_SAMPLE_FREQ_REQ),
> > > +			   div_u64(pmu->sample[gt_id][__I915_SAMPLE_FREQ_REQ].cur,
> > > 				   USEC_PER_SEC /* to MHz */);
> > > 			break;
> > > 		case I915_PMU_INTERRUPTS:
> > > diff --git a/drivers/gpu/drm/i915/i915_pmu.h b/drivers/gpu/drm/i915/i915_pmu.h
> > > index 33d80fbaab8bc..d20592e7db999 100644
> > > --- a/drivers/gpu/drm/i915/i915_pmu.h
> > > +++ b/drivers/gpu/drm/i915/i915_pmu.h
> > > @@ -127,7 +127,7 @@ struct i915_pmu {
> > > 	 * Only global counters are held here, while the per-engine ones are in
> > > 	 * struct intel_engine_cs.
> > > 	 */
> > > -	struct i915_pmu_sample sample[I915_PMU_MAX_GTS * __I915_NUM_PMU_SAMPLERS];
> > > +	struct i915_pmu_sample sample[I915_PMU_MAX_GTS][__I915_NUM_PMU_SAMPLERS];
> > > 	/**
> > > 	 * @sleep_last: Last time GT parked for RC6 estimation.
> > > 	 */