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

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Message-ID: <20090408110602.GA14687@one.firstfloor.org>
Date:	Wed, 8 Apr 2009 13:06:02 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Masami Hiramatsu <mhiramat@...hat.com>,
	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>,
	Andi Kleen <andi@...stfloor.org>, Avi Kivity <avi@...hat.com>,
	"Frank Ch. Eigler" <fche@...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

On Wed, Apr 08, 2009 at 12:10:56PM +0200, Ingo Molnar wrote:
> 
> * Masami Hiramatsu <mhiramat@...hat.com> wrote:
> 
> > > But can we consider it as a small problem, assuming that kprobes 
> > > are rarely intended for a massive use in once? I guess that 
> > > usually, not a lot of functions are probed simultaneously.
> > 
> > Hm, yes and no, systemtap may use massive kprobes, because it 
> > supports "wildcard" probes. However, optimizing in default may be 
> > acceptable.
> 
> 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.

-Andi
-- 
ak@...ux.intel.com -- Speaking for myself only.
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