linux-kernel - Re: [RFC][ PATCH -tip v2 0/7] kprobes: Kprobes jump optimization support

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Message-ID: <4A414F0D.3020805@redhat.com>
Date:	Tue, 23 Jun 2009 17:54:21 -0400
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	lkml <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jim Keniston <jkenisto@...ibm.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Christoph Hellwig <hch@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Anders Kaseorg <andersk@...lice.com>,
	Tim Abbott <tabbott@...lice.com>,
	systemtap <systemtap@...rces.redhat.com>,
	DLE <dle-develop@...ts.sourceforge.net>
Subject: Re: [RFC][ PATCH -tip v2 0/7] kprobes: Kprobes jump optimization
 support

Ingo Molnar wrote:
>> Ingo Molnar wrote:
>>> * Masami Hiramatsu <mhiramat@...hat.com> wrote:
>>>
>>>> o Usage
>>>>  Set CONFIG_OPTPROBES=y when building a kernel, then all *probes will be
>>>> optimized if possible.
>>> Should be default-y if KPROBES is enabled. I.e. we really only want 
>>> to disable it to debug potential issues.
>> Sure, thanks!
> 
> Plus i'd suggest a runtime control (a sysctl) as well - if it's not 
> too intrusive. Since this is an optional speedup feature, distros 
> can have this enabled and if there's some problem with it then it 
> can still be disabled in sysctl.conf, without having to rebuild the 
> kernel.

The runtime control is a good idea. Btw, current kprobes already has
a runtime disable interface under sysfs. Is there any reason that we'd
better to use sysctl instead of sysfs?


Thank you,

-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@...hat.com

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