linux-kernel - Re: [PATCH] arc: perf: Enable generic "cache-references" and "cache-misses" events

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Date:   Wed, 14 Sep 2016 10:53:48 -0700
From:   Vineet Gupta <vgupta@...opsys.com>
To:     Alexey Brodkin <Alexey.Brodkin@...opsys.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:     Arnaldo Carvalho de Melo <acme@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH] arc: perf: Enable generic "cache-references" and
 "cache-misses" events

On 08/26/2016 10:30 AM, Vineet Gupta wrote:
> On 08/25/2016 04:49 AM, Alexey Brodkin wrote:
>> ...
>>  	[PERF_COUNT_ARC_EDTLB] = "edtlb",	/* D-TLB Miss */
>>  	[PERF_COUNT_ARC_EITLB] = "eitlb",	/* I-TLB Miss */
>> +
>> +	[PERF_COUNT_HW_CACHE_REFERENCES] = "imemrdc",	/* Instr: mem read cached */
>> +	[PERF_COUNT_HW_CACHE_MISSES] = "dclm",		/* D-cache Load Miss */
> 
> I think this is duplicating a mistake we already have. I vaguely remember when
> doing some hackbench profiling last year with range based profiling confined to
> memset routine and saw that L1-dcache-misses was counting zero. This is because it
> only counts LD misses while memset only does ST.

So given that this is the best we got, I'm going to merge this anyways.

-Vineet

> 
> Performance counter stats for '/sbin/hackbench':
> 
>      0 L1-dcache-misses
>      0 L1-dcache-load-misses
>      1846082 L1-dcache-store-misses
> 
> 
> @PeterZ do you concur that is wrong and we ought to setup 2 counters to do this
> correctly ?
> 
> -Vineet
>