linux-kernel - Re: [PATCH -tip v3&10 02/18] kprobes: Introduce generic insn

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Message-ID: <4B8C7E23.1000302@redhat.com>
Date:	Mon, 01 Mar 2010 21:55:31 -0500
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	Mathieu Desnoyers <compudj@...stal.dyndns.org>
CC:	Ingo Molnar <mingo@...e.hu>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	lkml <linux-kernel@...r.kernel.org>,
	systemtap <systemtap@...rces.redhat.com>,
	DLE <dle-develop@...ts.sourceforge.net>,
	Jim Keniston <jkenisto@...ibm.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Christoph Hellwig <hch@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Anders Kaseorg <andersk@...lice.com>,
	Tim Abbott <tabbott@...lice.com>,
	Andi Kleen <andi@...stfloor.org>,
	Jason Baron <jbaron@...hat.com>
Subject: Re: [PATCH -tip v3&10 02/18] kprobes: Introduce generic insn_slot
 framework

Mathieu Desnoyers wrote:
> * Masami Hiramatsu (mhiramat@...hat.com) wrote:
>> Make insn_slot framework support various size slots.
>> Current insn_slot just supports one-size instruction buffer slot. However,
>> kprobes jump optimization needs larger size buffers.
> 
> OK, so you end up having one insn slot cache for kprobes and one insn
> slot (eventually) for the static jump patching (which needs larger
> instruction slots than kprobes). That seems like a good way to ensure
> you do not use more memory than necessary.
> 
> We could possibly go even further and automatically use the right insn
> slot cache given the size of the instruction entry that must be added (a
> bit like the memory allocator which have different pools for each
> allocation order).

Sure, that will be simpler interface.

> Possibly that using the terminology of "memory pools" rather than
> "cache" could be a better fit too. So what this really becomes is an
> instruction slot allocator and garbage collector.

Ah, right. It would be better to rename kprobe_insn_pool() :)

Thank you,



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