linux-kernel - Re: [RFC][PATCH 3/9] perf: export registerred pmus via sysfs

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Date:	Mon, 10 May 2010 13:43:11 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Lin Ming <ming.m.lin@...el.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	"eranian@...il.com" <eranian@...il.com>,
	"Gary.Mohr@...l.com" <Gary.Mohr@...l.com>,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	"arjan@...ux.intel.com" <arjan@...ux.intel.com>,
	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>,
	Paul Mackerras <paulus@...ba.org>,
	"David S. Miller" <davem@...emloft.net>,
	Russell King <rmk+kernel@....linux.org.uk>,
	Paul Mundt <lethal@...ux-sh.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [RFC][PATCH 3/9] perf: export registerred pmus via sysfs


* Peter Zijlstra <peterz@...radead.org> wrote:

> [...]
>
> This way we can create:
> 
> /sys/devices/system/cpu/cpuN/cpu_hardware_events 
>                              cpu_hardware_events/event_source_id
>                              cpu_hardware_events/cpu_cycles
>                              cpu_hardware_events/instructions
>                                                 /...
> 
> /sys/devices/system/cpu/cpuN/cpu_raw_events
>                              cpu_raw_events/event_source_id
> 
> 
> These would match the current PERF_TYPE_* values for compatibility
> 
> For new PMUs we can start a dynamic range of PERF_TYPE_ (say at 64k but
> that's not ABI and can be changed at any time, we've got u32 to play
> with).
> 
> For uncore this would result in:
> 
> /sys/devices/system/node/nodeN/node_raw_events
>                                node_raw_events/event_source_id
> 
> and maybe:
> 
> /sys/devices/system/node/nodeN/node_events
>                                node_events/event_source_id
>                                node_events/local_misses
>                                           /local_hits
>                                           /remote_misses
>                                           /remote_hits
>                                           /...
> 
> The software events and tracepoints and kprobes stuff we could hang off
> of /sys/kernel/ or something

Yeah, we really want a mechanism like this in place instead of continuing with 
the somewhat ad-hoc extensions to the event enumeration space.

One detail: i think we want one more level. Instead of:

 /sys/devices/system/node/nodeN/node_events
                                node_events/event_source_id
                                node_events/local_misses
                                           /local_hits
                                           /remote_misses
                                           /remote_hits
                                           /...

We want the individual events to be a directory, containing the event_id:

 /sys/devices/system/node/nodeN/node_events
                                node_events/event_source_id
                                node_events/local_misses/event_id
                                           /local_hits/event_id
                                           /remote_misses/event_id
                                           /remote_hits/event_id
                                           /...

The reason is that we want to keep our options open to add more attributes to 
individual events. (In fact extended attributes already exist for certain 
event classes - such as the 'format' info for tracepoints.)

Thanks,

	Ingo
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