linux-kernel - Re: [RFC][PROTO][PATCH -tip 0/7] kprobes: support jump optimization on x86

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Message-ID: <49DCBC12.3040700@redhat.com>
Date:	Wed, 08 Apr 2009 08:00:34 -0700
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	"Frank Ch. Eigler" <fche@...hat.com>
CC:	Andi Kleen <andi@...stfloor.org>, Ingo Molnar <mingo@...e.hu>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Jim Keniston <jkenisto@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Vegard Nossum <vegard.nossum@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Avi Kivity <avi@...hat.com>,
	Satoshi Oshima <satoshi.oshima.fk@...achi.com>,
	systemtap-ml <systemtap@...rces.redhat.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PROTO][PATCH -tip 0/7] kprobes: support jump optimization
 on x86

Frank Ch. Eigler wrote:
> On Wed, Apr 08, 2009 at 01:06:02PM +0200, Andi Kleen wrote:
>> [...]
>>> I'm curious: what is the biggest kprobe count you've ever seen, in 
>>> the field? 1000? 10,000? 100,000? More?
>> The limit is iirc how much memory the gcc compiling the probes program
>> consumes before running out of swap space.
> 
> On a machine with lots of free RAM, gcc will not hold itself back.  On
> my home server, a 40000-kprobe script compiled (pass 4) in about 4
> seconds using about 200MB RAM.

Hm, when 40,000 kprobes are optimized, it will consume less than 8MB ...
I guess that is acceptable for recent machines.

Thank you,

-- 
Masami Hiramatsu

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

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

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