linux-kernel - Re: [PATCH v2 2/6] powerpc/perf: Export memory hierarchy info to user space

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Date:   Mon, 13 Mar 2017 12:21:51 -0700
From:   Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
To:     Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>
Cc:     peterz@...radead.org, mpe@...erman.id.au,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Anna-Maria Gleixner <anna-maria@...utronix.de>,
        Daniel Axtens <dja@...ens.net>
Subject: Re: [PATCH v2 2/6] powerpc/perf: Export memory hierarchy info to
 user space

Madhavan Srinivasan [maddy@...ux.vnet.ibm.com] wrote:
> The LDST field and DATA_SRC in SIER identifies the memory hierarchy level
> (eg: L1, L2 etc), from which a data-cache miss for a marked instruction
> was satisfied. Use the 'perf_mem_data_src' object to export this
> hierarchy level to user space.
> 
<snip>

> diff --git a/arch/powerpc/include/asm/perf_event_server.h b/arch/powerpc/include/asm/perf_event_server.h
>  int isa207_get_constraint(u64 event, unsigned long *maskp, unsigned long *valp)
>  {
>  	unsigned int unit, pmc, cache, ebb;
> diff --git a/arch/powerpc/perf/isa207-common.h b/arch/powerpc/perf/isa207-common.h
> index cf9bd8990159..982542cce991 100644
> --- a/arch/powerpc/perf/isa207-common.h
> +++ b/arch/powerpc/perf/isa207-common.h
> @@ -259,6 +259,19 @@
>  #define MAX_ALT				2
>  #define MAX_PMU_COUNTERS		6
> 
> +#define ISA207_SIER_TYPE_SHIFT		15
> +#define ISA207_SIER_TYPE_MASK		(0x7ull << ISA207_SIER_TYPE_SHIFT)
> +
> +#define ISA207_SIER_LDST_SHIFT		1
> +#define ISA207_SIER_LDST_MASK		(0x7ull << ISA207_SIER_LDST_SHIFT)
> +
> +#define ISA207_SIER_DATA_SRC_SHIFT	53
> +#define ISA207_SIER_DATA_SRC_MASK	(0x7ull << ISA207_SIER_DATA_SRC_SHIFT)
> +
> +#define P(a, b)				PERF_MEM_S(a, b)

Madhavan, Peter,

Can we see if we can get the kernel to set 'perf_mem_data_src.val' in
endian-nuetral format?

With something like  (untested) in include/uapi/linux/perf_event.h

#define PERF_MEM_OP_NBITS	PERF_MEM_LVL_SHIFT
#define PERF_MEM_LVL_NBITS	PERF_MEM_SNOOP_SHIFT
#define PERF_MEM_SNOOP_NBITS	PERF_MEM_LOCK_SHIFT
#define PERF_MEM_TLB_NBITS	PERF_MEM_TLB_SHIFT

and here in arch/powerpc/perf/isa207-common.h

#define PERF_MEM_S_BE_SHIFT(a)	\
	(63 - PERF_MEM_##a##_NBITS - PERF_MEM_##a##_SHIFT)

#define PERF_MEM_S_BE(a, s)	\
		(((__u64)PERF_MEM_##a##_##s) << PERF_MEM_S_BE_SHIFT(a))

#define P(a, b)		PERF_MEM_S_BE(a, b)

Basically, have PERF_MEM_OP_NA be the right most bit and PERF_MEM_TLB_OS
the left most bit in perf_mem_data_src.val regardless of the endianness?

Sukadev