linux-kernel - Re: [PATCH v4 08/18] perf/x86: add memory profiling via PEBS Load Latency

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Date:	Mon, 7 Jan 2013 13:34:49 +0100
From:	Stephane Eranian <eranian@...gle.com>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Namhyung Kim <namhyung.kim@....com>
Subject: Re: [PATCH v4 08/18] perf/x86: add memory profiling via PEBS Load Latency

On Mon, Jan 7, 2013 at 11:11 AM, Jiri Olsa <jolsa@...hat.com> wrote:
> On Sun, Jan 06, 2013 at 09:37:25PM +0100, Stephane Eranian wrote:
>> On Sat, Jan 5, 2013 at 7:43 PM, Jiri Olsa <jolsa@...hat.com> wrote:
>> > On Thu, Dec 20, 2012 at 04:41:38PM +0100, Stephane Eranian wrote:
>> >> This patch adds support for memory profiling using the
>> >> PEBS Load Latency facility.
>> >>
>> >> Load accesses are sampled by HW and the instruction
>> >> address, data address, load latency, data source, tlb,
>> >> locked information can be saved in the sampling buffer
>> >> if using the PERF_SAMPLE_COST (for latency),
>> >
>> > PERF_SAMPLE_WEIGHT ?
>> >
>> No I switched to using Andi's PERF_SAMPLE_WEIGHT patch for this.
>> So it's PERF_SAMPLE_COST now.
>
Sorry, got it backwards. I was using PERF_SAMPLE_COST originally, but
then Andi added PERF_SAMPLE_WEIGHT. So I am using that one instead
now.


> Is it? I dont see PERF_SAMPLE_COST being used in the code..
>
>>
>> >> PERF_SAMPLE_ADDR, PERF_SAMPLE_DSRC types.
>> >>
>> >> To enable PEBS Load Latency, users have to use the
>> >> model specific event:
>> >> - on NHM/WSM: MEM_INST_RETIRED:LATENCY_ABOVE_THRESHOLD
>> >> - on SNB/IVB: MEM_TRANS_RETIRED:LATENCY_ABOVE_THRESHOLD
>> >>
>> >> To make things easier, this patch also exports a generic
>> >> alias via sysfs: mem-loads. It export the right event
>> >> encoding based on the host CPU and can be used directly
>> >> by the perf tool.
>> >>
>> >> Loosely based on Intel's Lin Ming patch posted on LKML
>> >> in July 2011.
>> >>
>> >> Signed-off-by: Stephane Eranian <eranian@...gle.com>
>> >
>> > SNIP
>> >
>> >> +/*
>> >> + * Map PEBS Load Latency Data Source encodings to generic
>> >> + * memory data source information
>> >> + */
>> >> +#define P(a, b) PERF_MEM_S(a, b)
>> >> +#define OP_LH (P(OP, LOAD) | P(LVL, HIT))
>> >> +#define SNOOP_NONE_MISS (P(SNOOP, NONE) | P(SNOOP, MISS))
>> >> +
>> >
>> > I checked Intel SDM 'Table 18-13. Data Source Encoding for Load Latency Record'
>> > and it seems to be different (below) at some points.. did you use another source?
>> >
>> Yeah, and the table is wrong in the SDM. What I have is correct and approved by
>> Intel.
>
> Is there any public link?
>
> thanks,
> jirka
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