linux-kernel - Re: [PATCH 1/1] perf tools: Add missing user space support for config1/config2

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Date:	Fri, 22 Apr 2011 21:54:45 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Andi Kleen <ak@...ux.intel.com>
Cc:	Arnaldo Carvalho de Melo <acme@...radead.org>,
	linux-kernel@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Stephane Eranian <eranian@...il.com>,
	Lin Ming <ming.m.lin@...el.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCH 1/1] perf tools: Add missing user space support for
 config1/config2


* Andi Kleen <ak@...ux.intel.com> wrote:

> On Fri, Apr 22, 2011 at 08:34:29AM +0200, Ingo Molnar wrote:
> > This needs to be a *lot* more user friendly. Users do not want to type in 
> > stupid hexa magic numbers to get profiling. We have moved beyond the oprofile 
> > era really.
> 
> I agree that the raw events are quite user unfriendly.
> 
> Unfortunately they are the way of life in perf -- unlike oprofile -- 
> currently if you want any CPU specific events like this.

Not sure where you take that blanket statement from, but no, raw events are not 
really the 'way of life' - judging by the various user feedback we get they 
come up pretty rarely.

The thing is, most people just use the default 'perf record' and that's it - 
they do not even care about a *single* event - they just want to profile their 
code somehow.

Then the second most popular event category are the generalized events, the 
ones you can see in perf list output:

  cpu-cycles OR cycles                       [Hardware event]
  instructions                               [Hardware event]
  cache-references                           [Hardware event]
  cache-misses                               [Hardware event]
  branch-instructions OR branches            [Hardware event]
  branch-misses                              [Hardware event]
  bus-cycles                                 [Hardware event]

  cpu-clock                                  [Software event]
  task-clock                                 [Software event]
  page-faults OR faults                      [Software event]
  minor-faults                               [Software event]
  major-faults                               [Software event]
  context-switches OR cs                     [Software event]
  cpu-migrations OR migrations               [Software event]
  alignment-faults                           [Software event]
  emulation-faults                           [Software event]

  L1-dcache-loads                            [Hardware cache event]
  L1-dcache-load-misses                      [Hardware cache event]
  L1-dcache-stores                           [Hardware cache event]
  L1-dcache-store-misses                     [Hardware cache event]
  L1-dcache-prefetches                       [Hardware cache event]
  L1-dcache-prefetch-misses                  [Hardware cache event]
  L1-icache-loads                            [Hardware cache event]
  L1-icache-load-misses                      [Hardware cache event]
  L1-icache-prefetches                       [Hardware cache event]
  L1-icache-prefetch-misses                  [Hardware cache event]
  LLC-loads                                  [Hardware cache event]
  LLC-load-misses                            [Hardware cache event]
  LLC-stores                                 [Hardware cache event]
  LLC-store-misses                           [Hardware cache event]
  LLC-prefetches                             [Hardware cache event]
  LLC-prefetch-misses                        [Hardware cache event]
  dTLB-loads                                 [Hardware cache event]
  dTLB-load-misses                           [Hardware cache event]
  dTLB-stores                                [Hardware cache event]
  dTLB-store-misses                          [Hardware cache event]
  dTLB-prefetches                            [Hardware cache event]
  dTLB-prefetch-misses                       [Hardware cache event]
  iTLB-loads                                 [Hardware cache event]
  iTLB-load-misses                           [Hardware cache event]
  branch-loads                               [Hardware cache event]
  branch-load-misses                         [Hardware cache event]

These are useful but are used less frequently.

Then come tracepoint based events - and as a distant last, come raw events. 
Yes, they raw events are useful occasionally, just like modifying applications 
via a hexa editor is useful occasionally. If done often we better abstract it 
out.

> Really to make sense out of all this you need per CPU full event lists.

To make sense out of what? You are making very sweeping yet vague statements.

> I have an own wrapper to make it more user friendly, but its functionality 
> should arguably migrate into perf.

Uhm, no - your patch seem to reintroduce oprofile's horrible events files. We 
really learned from that mistake and do not want to step back ...

Please see the detailed mails i wrote in this thread, what we want is to extend 
and improve existing generalizations of events. The useful bits of the offcore 
PMU fit nicely into that scheme.

Thanks,

	Ingo
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