Subject: Re: [RFC][PATCH] perf: Add a few generic stalled-cycles events

From: Robert Richter <[email-masked]>
Date: Tue, 16 Oct 2012 12:08:09 +0200

Sukadev,

On 15.10.12 17:55:34, Robert Richter wrote:
> On 11.10.12 18:28:39, Sukadev Bhattiprolu wrote:
> > +  { .type = PERF_TYPE_HARDWARE, .config = PERF_COUNT_HW_STALLED_CYCLES_FIXED_POINT },
> > +  { .type = PERF_TYPE_HARDWARE, .config = PERF_COUNT_HW_STALLED_CYCLES_LOAD_STORE },
> > +  { .type = PERF_TYPE_HARDWARE, .config = PERF_COUNT_HW_STALLED_CYCLES_INSTRUCTION_FETCH },
> > +  { .type = PERF_TYPE_HARDWARE, .config = PERF_COUNT_HW_STALLED_CYCLES_BRANCH },
> 
> Instead of adding new hardware event types I would prefer to use raw
> events in conjunction with sysfs, see e.g. the intel-uncore
> implementation. Something like:
> 
>  $ find /sys/bus/event_source/devices/cpu/events/
>  ...
>  /sys/bus/event_source/devices/cpu/events/stalled-cycles-fixed-point
>  /sys/bus/event_source/devices/cpu/events/stalled-cycles-load-store
>  /sys/bus/event_source/devices/cpu/events/stalled-cycles-instruction-fetch
>  /sys/bus/event_source/devices/cpu/events/stalled-cycles-branch
>  ...
>  $ cat /sys/bus/event_source/devices/cpu/events/stalled-cycles-fixed-point
>  event=0xff,umask=0x00
> 
> Perf tool works then out-of-the-box with:
> 
>  $ perf record -e cpu/stalled-cycles-fixed-point/ ...

I refer here to arch/x86/kernel/cpu/perf_event_intel_uncore.c (should
be in v3.7-rc1 or tip:perf/core). See the INTEL_UNCORE_EVENT_DESC()
macro and 'if (type->event_descs) ...' in uncore_type_init(). The code
should be reworked to be non-architectural.

PMU registration is implemented for a longer time already for all
architectures and pmu types:

 /sys/bus/event_source/devices/*

But

 /sys/bus/event_source/devices/*/events/

exists only for a small number of pmus. Perf tool support of this was
implemented with:

 a6146d5 perf/tool: Add PMU event alias support

-Robert

-- 
Advanced Micro Devices, Inc.
Operating System Research Center