Hi Fu,

Luotao Fu wrote:

Hi Wolfgang,

On Wed, Jun 18, 2008 at 10:07:05AM +0200, Wolfgang Grandegger wrote:

quoted

Hello,

I currently re-doing latency measurement with my TQM5200 board under  
Linux 2.6.25. With 2.6.24-rt1 "cyclictest -n -p80 -i1000 -t1" reported a  
maximum latency of 170us. With 2.6.25.4-rt5 I'm unable to reproduce such  
reasonable latencies. cyclictest shows quickly latencies up to 600 us.  
What has changed in the meantime? Any ideas how to get better latencies?

I've just brought up my mpc5200b board with 2.6.25.4-rt6 and ran for serveral
times cyclictest on it. I ran my tests with the same parameter as you mentioned.
As non-rt workload I ran an endless loop of "ls /". Based on the issue with rcu,
about which we discussed some times ago I also tried some combinations of
randomly chosen debugging options. So far I was not able to reproduce your
problem. Same for 2.6.25.4-rt5. 

Keep in mind that I'm running Linux on a rootfs mounted via NFS.

Could you possibly send me your kernel configuration, so I might probably have a
try here on my board?

Attached.

Thanks.

Wolfgang.