Messages in this thread | | | Date | Tue, 05 Aug 2008 17:40:54 +0200 | From | Wolfgang Grandegger <> | Subject | Re: 2.6.24-rc8-rt1: Strange latencies on mpc5200 powerpc - RCU issue? |
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Paul E. McKenney wrote: > On Wed, Jul 02, 2008 at 01:03:27PM +0200, Wolfgang Grandegger wrote: >> Wolfgang Grandegger wrote: >>> Steven Rostedt wrote: >>> There seems to be something in trace_mark() keeping latency low: >>> http://lxr.linux.no/linux+v2.6.24.4/include/linux/marker.h#L52 >>> I will follow your suggestions. >> I removed all "likely" and "unlikely" macros, but the latencies did not >> improve. Then I added >> >> preempt_disable(); >> preempt_enable(); >> >> at the two locations mentioned above, like trace_mark() does, and disabled >> CONFIG_RCU_TRACE. That helped to keep the latencies low, and it did for >> 2.6.25.8-rt7 as well. As I see it, adding preemption points seem to prevent >> high latencies. > > Interesting. Perhaps a preempt_enable_no_resched() somewhere that > should be preempt_enable()?
FYI, Thomas fixed the real problem a week ago and the patch went into 2.6.24.7-rt16. See his mail with the subject "2.6.24.7-rt16".
Wolfgang.
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