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

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Date:	Tue, 11 May 2010 17:40:45 +0800
From:	Lin Ming <ming.m.lin@...el.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	"eranian@...il.com" <eranian@...il.com>,
	"Gary.Mohr@...l.com" <Gary.Mohr@...l.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>,
	Will Deacon <will.deacon@....com>,
	Maynard Johnson <mpjohn@...ibm.com>,
	Carl Love <carll@...ibm.com>
Subject: Re: [RFC][PATCH 3/9] perf: export registerred pmus via sysfs

On Tue, 2010-05-11 at 17:12 +0800, Peter Zijlstra wrote:
> On Tue, 2010-05-11 at 17:03 +0800, Lin Ming wrote:
> > On Tue, 2010-05-11 at 16:50 +0800, Peter Zijlstra wrote:
> > > On Tue, 2010-05-11 at 16:20 +0800, Lin Ming wrote:
> > > 
> > > > How will this sysfs interface be used for userspace tool?
> > > > 
> > > >  /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
> > > > 
> > > > For example, to monitor node event local_misses on node 0, does it work
> > > > as below?
> > > > 
> > > > 1. perf top -e local_misses -n 0 (-n 0 means node 0)
> > > > 
> > > > 2. read /sys/devices/system/node/node0/node_events/event_source_id to
> > > > get the pmu_id
> > > > 
> > > > 3. read /sys/devices/system/node/node0/node_events/local_misses/event_id
> > > > to get the event_id
> > > > 
> > > > 4. event_attr::pmu_id=pmu_id, event::config=event_id
> > > > 
> > > > 5. other setting...
> > > > 
> > > > 6. call syscall perf_event_open(....)
> > > 
> > > No, you'll use event_source_id as perf_event_attr::type, use event_id as
> > > perf_event_attr::config and then use a cpu-wide counter on a cpu
> > > contained in node0.
> > 
> > Is event_source_id a link to event_source class?
> 
> No its an attribute of said class.
> 
> > For example, 2 event sources on Nehalem
> > /sys/class/event_sources/core_pmu
> > /sys/class/event_sources/uncore_pmu
> > 
> > Then,
> > /sys/devices/system/node/nodeN/node_events/event_source_id is a link
> > to /sys/class/event_sources/uncore_pmu.
> 
> > /sys/devices/system/cpu/cpuN/cpu_hardware_events/event_source_id is a
> > link to /sys/class/event_sources/core_pmu.
> 
> The other way around, look in /sys/class/*/, they're all symlinks.

/sys/devices/system/cpu/cpu0/cpu_hw_events/*
/sys/devices/system/cpu/cpu0/cpu_hw_cache_events/*
/sys/devices/system/cpu/cpu0/cpu_raw_events/*
....
....
/sys/devices/system/cpu/cpuN/cpu_hw_events/*
/sys/devices/system/cpu/cpuN/cpu_hw_cache_events/*
/sys/devices/system/cpu/cpuN/cpu_raw_events/*

Is /sys/class/event_sources/* looks like,

/sys/class/event_sources/cpu_hw_events0
-> /sys/devices/system/cpu/cpu0/cpu_hw_events
...
/sys/class/event_sources/cpu_hw_eventsN
-> /sys/devices/system/cpu/cpuN/cpu_hw_events

/sys/class/event_sources/cpu_hw_cache_events0
-> /sys/devices/system/cpu/cpu0/cpu_hw_events
...
/sys/class/event_sources/cpu_hw_cache_eventsN
-> /sys/devices/system/cpu/cpuN/cpu_hw_events

?

> 
> > And, the event_source_id
> > #cat /sys/class/event_sources/core_pmu
> > 0
> 
> > #cat /sys/class/event_sources/uncore_pmu
> > 1
> 
> You can't cat a directory. You'd cat something
> like: /sys/class/event_sources/core_pmu/event_source_id
> 
> And they would contain PERF_TYPE_* like things.
> 
> So for the current CPU PMUs we'd already create 3 event classes,
> cpu_hw_events, cpu_hw_cache_events, cpu_raw_events, with resp.
> event_source_id of 0, 3 and 4.
> 
> The new PMUs will use a dynamic range that starts at PERF_TYPE_MAX.

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