linux-kernel - Re: [PATCH 00/12] perf lock: New subcommand "perf lock", for analyzing lock statistics

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Date:	Mon, 25 Jan 2010 15:48:03 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Hitoshi Mitake <mitake@....info.waseda.ac.jp>
Cc:	Jason Baron <jbaron@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org, Paul Mackerras <paulus@...ba.org>,
	Tom Zanussi <tzanussi@...il.com>,
	Steven Rostedt <srostedt@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Greg Kroah-Hartman <gregkh@...e.de>
Subject: Re: [PATCH 00/12] perf lock: New subcommand "perf lock", for 
 analyzing lock statistics

On Mon, 2010-01-25 at 23:15 +0900, Hitoshi Mitake wrote:
> 
> As Peter told, this patch series depends on lockdep.
> But, checking dependency and tracing lock events are
> essentially different things. So I think dividing these is possible.

Still you need quite a lot of instrumentation at the actual lock sites,
not something you'd want to have on your production machine.

> But, perf depends on debugfs.
> I don't know about production box well,
> does your production box turns on debugfs?
> It seems that debugfs is not a thing for production box...

debugfs isn't a problem to have.

> And I'm interesting in in-kernel histogram of locks.
> Is there requirement of it?
> I have some ideas (not done yet, completely).

No real concrete ideas yet.. One possibility is to add a range,
bucket_size tuple to perf_event_attr and store the histrogram in the
mmap() area instead of samples.

One difficulty is how to specify what to make that histogram over.

Anyway, its all open still..

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