Date: Sat, 9 Aug 2008 16:42:11 +0200 (CEST)
From: Bodo Eggert <7eggert@gmx.de>
To: Steven Rostedt <rostedt@goodmis.org>
cc: Bodo Eggert <7eggert@gmx.de>, Andi Kleen <andi@firstfloor.org>,
       Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>,
       LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@elte.hu>,
       Thomas Gleixner <tglx@linutronix.de>,
       Peter Zijlstra <peterz@infradead.org>,
       Andrew Morton <akpm@linux-foundation.org>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       David Miller <davem@davemloft.net>, Roland McGrath <roland@redhat.com>,
       Ulrich Drepper <drepper@redhat.com>,
       Rusty Russell <rusty@rustcorp.com.au>,
       Jeremy Fitzhardinge <jeremy@goop.org>,
       Gregory Haskins <ghaskins@novell.com>,
       Arnaldo Carvalho de Melo <acme@redhat.com>,
       "Luis Claudio R. Goncalves" <lclaudio@uudg.org>,
       Clark Williams <williams@redhat.com>
Subject: Re: [PATCH 0/5] ftrace: to kill a daemon
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On Sat, 9 Aug 2008, Steven Rostedt wrote:
> On Sat, 9 Aug 2008, Bodo Eggert wrote:
> > Steven Rostedt <rostedt@goodmis.org> wrote:
> > > On Sat, 9 Aug 2008, Andi Kleen wrote:
> > >> Steven Rostedt <rostedt@goodmis.org> writes:

> > >> > I'm stubborn, I want to get it right _and_ keep it fast.
> > >> 
> > >> For me it would seem better to just not use two part 5 byte nops
> > >> instead of adding such hacks.  I doubt there are that many of them
> > >> anyways. I bet you won't be able to measure any difference between the
> > >> different nop types in any macro benchmark.
> > > 
> > > I wish we had a true 5 byte nop. The alternative is a jmp 0, which is
> > > measurable.
> > 
> > Did you try short jumps? (0xeb 0x03 0x?? 0x?? 0x??)
> 
> What would those last three bytes be?

Anything, since the CPU will ignore them.

My hope is that different kinds of jump will behaver differently,
but I fear the side effect of the jmp (reread memory in case of 
self-modifying code) will cause the CPU to slow down anyway.
-- 
Is reading in the bathroom considered Multitasking?
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