Re: 2.6.19-rc6-rt4, changed yum repository

From: Robert Schwebel
Date: Sun Nov 19 2006 - 09:46:56 EST


Ingo,

On Sat, Nov 18, 2006 at 05:30:32PM +0100, Ingo Molnar wrote:
> i've released the 2.6.18-rc6-rt4 tree, which can be downloaded from
> the usual place:

I have problems runinng cyclictest on later -rt kernels, up to -rt4.

This is a Dell Latitude D610, with Pentium M & ICH6 chipset.

Symptoms:

- "cyclictest -n -p 90 -t 4" is just "running upwards"

With 2.6.18-rt5 it looked like this, much better:

isonoe:/home/rsc/tmp/rtpreempt/cyclictest-0.11# ./cyclictest -n -t 4 -p 90 -l 1000
1.51 0.99 0.41 1/117 9885

T: 0 ( 9802) P:90 I: 1000 C: 1000 Min: 7 Act: 11 Avg: 16 Max: 561
T: 1 ( 9803) P:89 I: 1500 C: 671 Min: 7 Act: 11 Avg: 15 Max: 498
T: 2 ( 9804) P:88 I: 2000 C: 504 Min: 7 Act: 11 Avg: 16 Max: 533
T: 3 ( 9805) P:87 I: 2500 C: 403 Min: 6 Act: 11 Avg: 13 Max: 394

- Using a relative timer (-r), I get huge latencies:

isonoe:/home/rsc/tmp/rtpreempt/cyclictest-0.11# ./cyclictest -n -p 90 -t 4 -r -l 1000
0.47 0.76 0.61 3/128 16112

T: 0 (15901) P:90 I: 1000 C: 1000 Min: 2963 Act: 2990 Avg: 4334 Max: 7039
T: 1 (15902) P:89 I: 1500 C: 667 Min: 4003 Act: 6495 Avg: 6492 Max: 6541
T: 2 (15903) P:88 I: 2000 C: 667 Min: 3498 Act: 5995 Avg: 5993 Max: 6041
T: 3 (15904) P:87 I: 2500 C: 667 Min: 5433 Act: 5488 Avg: 5498 Max: 6898

This is with "lapic lapictimer" on the kernel commandline. I've manually
switched the clocksource from pit to tsc:

isonoe:/sys/devices/system/clocksource/clocksource0# cat available_clocksource
jiffies tsc pit
isonoe:/sys/devices/system/clocksource/clocksource0# cat current_clocksource
tsc

Some related dmesg output:

Kernel command line: root=/dev/sda7 ro lapic lapictimer
Found and enabled local APIC!
mapped APIC to ffffd000 (fee00000)
...
WARNING: experimental RCU implementation.
Clock event device pit configured with caps set: 07
...
Clock event device pit new caps set: 03
Clock event device lapic configured with caps set: 04
...
Time: pit clocksource has been installed.
...
*****************************************************************************
* *
* REMINDER, the following debugging options are turned on in your .config: *
* *
* CONFIG_CRITICAL_PREEMPT_TIMING *
* CONFIG_CRITICAL_IRQSOFF_TIMING *
* CONFIG_FUNCTION_TRACE *
* *
* they may increase runtime overhead and latencies. *
* *
*****************************************************************************

Last time this machine worked was with 2.6.18-rt5, 2.6.18-rt7 didn't work any
more. If it is helpful, I can do some further boot tests to find out which
patch broke it.

Robert
--
Dipl.-Ing. Robert Schwebel | http://www.pengutronix.de
Pengutronix - Linux Solutions for Science and Industry
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