linux-kernel - Re: [PATCH 1/7] perf: introduce raw_type attribute to specify the type of a raw sample

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Message-ID: <4BF46000.20203@linux.vnet.ibm.com>
Date:	Wed, 19 May 2010 15:02:40 -0700
From:	Corey Ashford <cjashfor@...ux.vnet.ibm.com>
To:	Robert Richter <robert.richter@....com>
CC:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>,
	Stephane Eranian <eranian@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Lin Ming <ming.m.lin@...el.com>
Subject: Re: [PATCH 1/7] perf: introduce raw_type attribute to specify the
 type of a raw sample

Hi Robert,

On 5/19/2010 2:20 PM, Robert Richter wrote:
> This patch introduces a method to specify the type of a raw sample.
> This can be used to setup hardware events other than generic
> performance counters by passing special config data to the pmu. The
> config data can be interpreted different from generic events and thus
> can be used for other purposes.
> 
> The raw_type attribute is an extension of the ABI. It reuses the
> unused bp_type space for this. Generic performance counters can be
> setup by setting the raw_type attribute to null. Thus special raw
> events must have a type other than null.
> 
> Raw types can be defined as needed for cpu models or architectures.
> To keep backward compatibility all architectures must return an error
> for an event with a raw_type other than null that is not supported.
> 
> E.g., raw_type can be used to setup IBS on an AMD cpu. IBS is not
> common to pmu features from other vendors or architectures. The pmu
> must be setup with a special config value. Sample data is returned in
> a certain format back to the userland. An IBS event is created by
> setting a raw event and encoding the IBS type in raw_type. The pmu
> handles this raw event then and passes raw sample data back.
> 
> Raw type could be architecure specific, e.g. for x86:
> 
> enum perf_raw_type {
>         PERF_RAW_PERFCTR                        = 0,
>         PERF_RAW_IBS_FETCH                      = 1,
>         PERF_RAW_IBS_OP                         = 2,
> 
>         PERF_RAW_MAX,
> };
> 
> Null is the architecture's default, meaning for x86 a perfctr.
> 
> Maybe the raw type definition could also be part of the ABI with one
> definition for all architectures.
> 
> To use raw events with perf, the raw event syntax could be suffixed by
> the type (as for breakpoints):
> 
>    -e rNNN[:TYPE]
> 
> Example:
> 
>  perf record -e r186A:1          # ... meaning IBS fetch, cycle count 100000
>  perf record -e r0:1 -c 100000   # ... the same
> 
> Or with named types:
> 
>  perf record -e r186A:IBS_FETCH ...
>  perf record -e r0:IBS_FETCH -c 100000 ...

Should this raw value have been 186A0 instead of 186A?

Where is the named type translation coming from?  Is this something that needs to be hard-coded into perf?

Have you looked at Lin Ming's patch series?  I think it offers another way to support IBS and other arch-specific and off-chip PMUs in a more general way, though it's not quite fully-baked yet.

- Corey

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