linux-kernel - Re: [PATCH v2 14/16] perf tools: add new mem command for memory access profiling

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Date:	Tue, 6 Nov 2012 12:44:46 -0300
From:	Arnaldo Carvalho de Melo <acme@...hat.com>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	linux-kernel@...r.kernel.org, peterz@...radead.org, mingo@...e.hu,
	ak@...ux.intel.com, jolsa@...hat.com, namhyung.kim@....com
Subject: Re: [PATCH v2 14/16] perf tools: add new mem command for memory
 access profiling

Em Mon, Nov 05, 2012 at 02:51:01PM +0100, Stephane Eranian escreveu:
> +
> +	if (strcmp(mem_operation, MEM_OPERATION_LOAD))
> +		sprintf(event, "cpu/mem-stores/pp");
> +	else
> +		sprintf(event, "cpu/mem-loads/pp");
> +

Fails for me on a Sandy Bridge notebook:

[root@...dy ~]# perf mem -t store record -a
Error:
'precise' request may not be supported. Try removing 'p' modifier

So if I manually fall back to a less precise mode:

[root@...dy ~]# perf record -g -a -e cpu/mem-stores/p
Error:
'precise' request may not be supported. Try removing 'p' modifier
[root@...dy ~]#

Still can't, manually fall back a one more level:

[root@...dy ~]# perf record -g -a -e cpu/mem-stores/
^C[ perf record: Woken up 25 times to write data ]
[ perf record: Captured and wrote 7.419 MB perf.data (~324160 samples) ]

Yay, got some numbers.

smpboot: CPU0: Intel(R) Core(TM) i7-2920XM CPU @ 2.50GHz (fam: 06, model: 2a, stepping: 07)
Performance Events: PEBS fmt1+, 16-deep LBR, SandyBridge events, Intel PMU driver.
perf_event_intel: PEBS disabled due to CPU errata, please upgrade microcode
... version:                3
... bit width:              48
... generic registers:      4
... value mask:             0000ffffffffffff
... max period:             000000007fffffff
... fixed-purpose events:   3
... event mask:             000000070000000f
Disabled fast string operations
NMI watchdog: enabled on all CPUs, permanently consumes one hw-PMU counter.

Do you have any test program you use to test if the results make sense that you
could share?

I could then try to shape it into a new 'perf test' entry that would test
if requesting this event and then doing synthetic testing would produce 
the experted numbers or in a acceptable range.

One suggestion for such new features, examples of use with the resulting output
looks great on changeset logs :-)

Ah, I recall seeing some, but that was on the patchset cover letter,
that doesn't get inserted in the git changelog history, will look at those
now.

- Arnaldo
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