linux-kernel - Re: linux-next: add utrace tree

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Message-ID: <y0mr5p893tw.fsf@fche.csb>
Date:	Fri, 29 Jan 2010 13:13:47 -0500
From:	fche@...hat.com (Frank Ch. Eigler)
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Jim Keniston <jkenisto@...ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Tom Tromey <tromey@...hat.com>,
	Kyle Moffett <kyle@...fetthome.net>,
	Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Fr??d??ric Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	linux-next@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>,
	utrace-devel@...hat.com, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: linux-next: add utrace tree

Ingo Molnar <mingo@...e.hu> writes:

> [...] So, to sum it up: utrace XOL, which is rather complex already,
> needs even more complexity (which is not yet implemented) than the
> much simpler common-case emulator approach i outlined, just to break
> even with the performance of the much simpler approach. [...]

Is it an uncontroversial claim that emulation of CISC instructions
should perform better than their native execution, followed by an int3
(as in the simplest working scheme) or boosting (as done by kprobes)?
>From my experience with simulators, "simple" software emulation of
cpus can be hundreds of times slower or worse than native execution.

- FChE
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