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Date: Tue, 20 Jul 2010 17:19:20 +0200
From: Robert Richter <robert.richter@amd.com>
To: Lin Ming <ming.m.lin@intel.com>
CC: Corey Ashford <cjashfor@linux.vnet.ibm.com>, Ingo Molnar <mingo@elte.hu>,
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Subject: Re: [rfc] Describe events in a structured way via sysfs
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References: <20100624093625.GA26931@elte.hu>
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On 20.07.10 01:48:28, Lin Ming wrote:
 The caller reads config and type and pass them into perf_event_attr.
> 
> 1. Hardware events
> /sys/devices/system/cpu/cpu0...cpuN/events
> |-- L1-dcache-load-misses  ===> event name
> |   |-- config             ===> config value for the event
> |   `-- type               ===> event type

Wouldn't it be much easier to have a unique sysfs id (could be an
u64):

> |-- L1-dcache-load-misses  ===> event name
> |   `-- id                 ===> event id

... and then extend the syscall to enable an event by its sysfs id:

            memset(&attr, 0, sizeof(attr));
            attr.type        = PERF_TYPE_SYSFS;
            attr.sysfs_id    = sysfs_id;
            attr.sample_type = PERF_SAMPLE_CPU | PERF_SAMPLE_RAW;
            attr.config      = config;
	    ...

The kerrnel then knows which event is meant and the don't have to
provide event specific paramaters such as type/config that requires an
event specific setup. The advantage would be that we can open an event
file descriptor of every kind of event in a standardized way.

-Robert

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