linux-kernel - Re: disabling group leader perf

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Message-ID: <20100912191429.GA27440@elf.ucw.cz>
Date:	Sun, 12 Sep 2010 21:14:29 +0200
From:	Pavel Machek <pavel@....cz>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Avi Kivity <avi@...hat.com>, Pekka Enberg <penberg@...helsinki.fi>,
	Tom Zanussi <tzanussi@...il.com>,
	Fr?d?ric Weisbecker <fweisbec@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-perf-users@...r.kernel.org,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: disabling group leader perf_event

On Sun 2010-09-12 20:48:43, Ingo Molnar wrote:
> 
> * Avi Kivity <avi@...hat.com> wrote:
> 
> >  On 09/12/2010 08:46 AM, Pavel Machek wrote:
> > >  1- Most (least abstract) specific code: a block of bytecode in the form
> > >     of a simplified, executable, kernel-checked x86 machine code block -
> > >     this is also the fastest form. [yes, this is actually possible.]
> > >Well... if we want to be a bit x86-entric.... can we just reuse ACPI
> > >interpretter?
> > 
> > I hope this was a joke, ACPI won the academy awards for ugliness, 
> > ..., bad specification, non-generality, and 

As did i386 instruction set :-).

> It also combines the worst of the two worlds: it's the most specific 
> type of code (almost like assembly), but has a very slow interpreter.
> 
> With 'x86 bytecode' the main (and pretty much only) point is to be able 
> to execute the code as-is, once checked.
> 
> But, as i explained it before, i only consider it a theoretical 
> possibility and i think that abstract code (such as ASCII text C source 
> code) is a better solution.

Compiler in kernel?

I'm not sure I like that one. Yes, ACPI interpreter is slow, but it is
simple, already in kernel, and there are already tools to compile into
it...

While it may be ugly, I believe it is better than either i386
verifier, compiler in the kernel, or yet another interpretter...

									Pavel

-- 
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