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Date: Wed, 09 Jul 2008 15:15:01 +0200 From: Wolfgang Grandegger <wg@...ndegger.com> To: Luotao Fu <l.fu@...gutronix.de> CC: 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 Fu (without n) Luotao Fu wrote: > Hi Wolfgang, > > Wolfgang Grandegger wrote: >> Hi Fun, > > What's so funny? ;-) Ah, oh, just a funny typo ;-). > [...] > >> But as Steven pointed out, the preempt_enable_noresched at that place >> might be illegal, anyway. In 2.6.25-rt, trace_mark() is no longer >> used and I do not see an improvement with CONFIG_RCU_TRAC any more. >> Latencies go up to 600us. I also tried with CONFIG_RCU_BOOST >> disabled, but it did not improve the latencies. Actually, I still >> measure significantly different latencies with 2.6.24.4-rt4, >> 2.6.24.7-rt14 and 2.6.25.8-rt7, which is quite frustrating. As you >> seem not be able to reproduce my high latencies, I wonder if there >> are some toolchain or glibc related issues. > > I took a quick look into the rcppreempt boost stuff in 2.6.24-rt and > 2.6.25-rt. As you have mentioned, trace_mark is no more used in > 2.6.24-rt. Instead of that flags are used to detect if the task is > preempted. It might indeed probably be some toolchain issue. > My powerpc toolchain I'm using here contains gcc 4.1.2 and glibc 2.5 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? Wolfgang. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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