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 11:11:13 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	Stephane Eranian <eranian@...gle.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 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.

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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