Re: [PATCH V2 1/5] powerpc/perf: Expose processor pipeline stage cycles using PERF_SAMPLE_WEIGHT_STRUCT

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Wed, Mar 24, 2021 at 10:05:23AM +0530, Madhavan Srinivasan escreveu:
> 
> On 3/22/21 8:27 PM, Athira Rajeev wrote:
> > Performance Monitoring Unit (PMU) registers in powerpc provides
> > information on cycles elapsed between different stages in the
> > pipeline. This can be used for application tuning. On ISA v3.1
> > platform, this information is exposed by sampling registers.
> > Patch adds kernel support to capture two of the cycle counters
> > as part of perf sample using the sample type:
> > PERF_SAMPLE_WEIGHT_STRUCT.
> > 
> > The power PMU function 'get_mem_weight' currently uses 64 bit weight
> > field of perf_sample_data to capture memory latency. But following the
> > introduction of PERF_SAMPLE_WEIGHT_TYPE, weight field could contain
> > 64-bit or 32-bit value depending on the architexture support for
> > PERF_SAMPLE_WEIGHT_STRUCT. Patches uses WEIGHT_STRUCT to expose the
> > pipeline stage cycles info. Hence update the ppmu functions to work for
> > 64-bit and 32-bit weight values.
> > 
> > If the sample type is PERF_SAMPLE_WEIGHT, use the 64-bit weight field.
> > if the sample type is PERF_SAMPLE_WEIGHT_STRUCT, memory subsystem
> > latency is stored in the low 32bits of perf_sample_weight structure.
> > Also for CPU_FTR_ARCH_31, capture the two cycle counter information in
> > two 16 bit fields of perf_sample_weight structure.
> 
> Changes looks fine to me.

You mean just the kernel part or can I add your Reviewed-by to all the
patchset?
 
> Reviewed-by: Madhavan Srinivasan <maddy@linux.ibm.com>
> 
> 
> > Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
> > ---
> >   arch/powerpc/include/asm/perf_event_server.h |  2 +-
> >   arch/powerpc/perf/core-book3s.c              |  4 ++--
> >   arch/powerpc/perf/isa207-common.c            | 29 +++++++++++++++++++++++++---
> >   arch/powerpc/perf/isa207-common.h            |  6 +++++-
> >   4 files changed, 34 insertions(+), 7 deletions(-)
> > 
> > diff --git a/arch/powerpc/include/asm/perf_event_server.h b/arch/powerpc/include/asm/perf_event_server.h
> > index 00e7e671bb4b..112cf092d7b3 100644
> > --- a/arch/powerpc/include/asm/perf_event_server.h
> > +++ b/arch/powerpc/include/asm/perf_event_server.h
> > @@ -43,7 +43,7 @@ struct power_pmu {
> >   				u64 alt[]);
> >   	void		(*get_mem_data_src)(union perf_mem_data_src *dsrc,
> >   				u32 flags, struct pt_regs *regs);
> > -	void		(*get_mem_weight)(u64 *weight);
> > +	void		(*get_mem_weight)(u64 *weight, u64 type);
> >   	unsigned long	group_constraint_mask;
> >   	unsigned long	group_constraint_val;
> >   	u64             (*bhrb_filter_map)(u64 branch_sample_type);
> > diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
> > index 766f064f00fb..6936763246bd 100644
> > --- a/arch/powerpc/perf/core-book3s.c
> > +++ b/arch/powerpc/perf/core-book3s.c
> > @@ -2206,9 +2206,9 @@ static void record_and_restart(struct perf_event *event, unsigned long val,
> >   						ppmu->get_mem_data_src)
> >   			ppmu->get_mem_data_src(&data.data_src, ppmu->flags, regs);
> > -		if (event->attr.sample_type & PERF_SAMPLE_WEIGHT &&
> > +		if (event->attr.sample_type & PERF_SAMPLE_WEIGHT_TYPE &&
> >   						ppmu->get_mem_weight)
> > -			ppmu->get_mem_weight(&data.weight.full);
> > +			ppmu->get_mem_weight(&data.weight.full, event->attr.sample_type);
> >   		if (perf_event_overflow(event, &data, regs))
> >   			power_pmu_stop(event, 0);
> > diff --git a/arch/powerpc/perf/isa207-common.c b/arch/powerpc/perf/isa207-common.c
> > index e4f577da33d8..5dcbdbd54598 100644
> > --- a/arch/powerpc/perf/isa207-common.c
> > +++ b/arch/powerpc/perf/isa207-common.c
> > @@ -284,8 +284,10 @@ void isa207_get_mem_data_src(union perf_mem_data_src *dsrc, u32 flags,
> >   	}
> >   }
> > -void isa207_get_mem_weight(u64 *weight)
> > +void isa207_get_mem_weight(u64 *weight, u64 type)
> >   {
> > +	union perf_sample_weight *weight_fields;
> > +	u64 weight_lat;
> >   	u64 mmcra = mfspr(SPRN_MMCRA);
> >   	u64 exp = MMCRA_THR_CTR_EXP(mmcra);
> >   	u64 mantissa = MMCRA_THR_CTR_MANT(mmcra);
> > @@ -296,9 +298,30 @@ void isa207_get_mem_weight(u64 *weight)
> >   		mantissa = P10_MMCRA_THR_CTR_MANT(mmcra);
> >   	if (val == 0 || val == 7)
> > -		*weight = 0;
> > +		weight_lat = 0;
> >   	else
> > -		*weight = mantissa << (2 * exp);
> > +		weight_lat = mantissa << (2 * exp);
> > +
> > +	/*
> > +	 * Use 64 bit weight field (full) if sample type is
> > +	 * WEIGHT.
> > +	 *
> > +	 * if sample type is WEIGHT_STRUCT:
> > +	 * - store memory latency in the lower 32 bits.
> > +	 * - For ISA v3.1, use remaining two 16 bit fields of
> > +	 *   perf_sample_weight to store cycle counter values
> > +	 *   from sier2.
> > +	 */
> > +	weight_fields = (union perf_sample_weight *)weight;
> > +	if (type & PERF_SAMPLE_WEIGHT)
> > +		weight_fields->full = weight_lat;
> > +	else {
> > +		weight_fields->var1_dw = (u32)weight_lat;
> > +		if (cpu_has_feature(CPU_FTR_ARCH_31)) {
> > +			weight_fields->var2_w = P10_SIER2_FINISH_CYC(mfspr(SPRN_SIER2));
> > +			weight_fields->var3_w = P10_SIER2_DISPATCH_CYC(mfspr(SPRN_SIER2));
> > +		}
> > +	}
> >   }
> >   int isa207_get_constraint(u64 event, unsigned long *maskp, unsigned long *valp, u64 event_config1)
> > diff --git a/arch/powerpc/perf/isa207-common.h b/arch/powerpc/perf/isa207-common.h
> > index 1af0e8c97ac7..fc30d43c4d0c 100644
> > --- a/arch/powerpc/perf/isa207-common.h
> > +++ b/arch/powerpc/perf/isa207-common.h
> > @@ -265,6 +265,10 @@
> >   #define ISA207_SIER_DATA_SRC_SHIFT	53
> >   #define ISA207_SIER_DATA_SRC_MASK	(0x7ull << ISA207_SIER_DATA_SRC_SHIFT)
> > +/* Bits in SIER2/SIER3 for Power10 */
> > +#define P10_SIER2_FINISH_CYC(sier2)	(((sier2) >> (63 - 37)) & 0x7fful)
> > +#define P10_SIER2_DISPATCH_CYC(sier2)	(((sier2) >> (63 - 13)) & 0x7fful)
> > +
> >   #define P(a, b)				PERF_MEM_S(a, b)
> >   #define PH(a, b)			(P(LVL, HIT) | P(a, b))
> >   #define PM(a, b)			(P(LVL, MISS) | P(a, b))
> > @@ -278,6 +282,6 @@ int isa207_get_alternatives(u64 event, u64 alt[], int size, unsigned int flags,
> >   					const unsigned int ev_alt[][MAX_ALT]);
> >   void isa207_get_mem_data_src(union perf_mem_data_src *dsrc, u32 flags,
> >   							struct pt_regs *regs);
> > -void isa207_get_mem_weight(u64 *weight);
> > +void isa207_get_mem_weight(u64 *weight, u64 type);
> >   #endif

-- 

- Arnaldo