linux-kernel - Re: 2.6.24-rc8-rt1: Strange latencies on mpc5200 powerpc

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Message-ID: <20080709145217.GB30586@pengutronix.de>
Date:	Wed, 9 Jul 2008 16:52:17 +0200
From:	Luotao Fu <l.fu@...gutronix.de>
To:	Wolfgang Grandegger <wg@...ndegger.com>
Cc:	Luotao Fu <l.fu@...gutronix.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	RT <linux-rt-users@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: 2.6.24-rc8-rt1: Strange latencies on mpc5200 powerpc - RCU
	issue?

Hi Wolfgang,
On Wed, Jul 09, 2008 at 03:15:01PM +0200, Wolfgang Grandegger wrote:
> Hi Fu (without n)
>
....
> OK, in the past you have been able to reproduce the high latencies with  
> 2.6.24-rt1 and CONFIG_RCU_TRACE disabled, IIRC. Did you use a different  
> toolchain at that time?
>

Nope. As mentioned above, trace_mark() does some "real" works (what ever it is.),
while the new mechahnismen use flags to remember the state of preemption. Maybe
something here got optimized away? I take for grant, that you use gcc in your
toolchain. Which version do you have?

cheers
Fu
-- 
   Dipl.-Ing. Luotao Fu | Phone: +49-5121-206917-3
Pengutronix - Linux Solutions for Science and Industry
Entwicklungszentrum Nord     http://www.pengutronix.de


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