lkml.org 
[lkml]   [2008]   [Aug]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: 2.6.24-rc8-rt1: Strange latencies on mpc5200 powerpc - RCU issue?
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.


\
 
 \ /
  Last update: 2008-08-05 17:41    [W:3.470 / U:0.308 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site