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 23:15:33 +0900
From:	Hitoshi Mitake <mitake@....info.waseda.ac.jp>
To:	Jason Baron <jbaron@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	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

Hi Jason, thanks for your reply!

On Sat, Jan 23, 2010 at 01:42, Jason Baron <jbaron@...hat.com> wrote:
> On Fri, Jan 22, 2010 at 10:39:01PM +0900, Hitoshi Mitake wrote:
>> Adding new subcommand "perf lock" to perf.
>>
>
> looks like a really intresting patch! Does this patch mean that we can
> potentially remove CONFIG_LOCK_STAT, now that the functionality is
> available via 'perf'? Another desire for me has been to able to run
> lockstat on production box. This has not been possible before without
> incurring the performance penalty of lockdep. however, with 'perf' tools
> ability to be turned on an off, perhaps there is (or we can build) a
> mode for lockdep that is lower overhead for this usecase?
>

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.

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...

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

Thanks,
	Hitoshi
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