Clark Williams schrieb:
On Tue, 9 Feb 2010 07:41:58 +0000 (UTC)
Max Miller <mxmr@xxxxxxx> wrote:
Hello,
im am using the PREEMPT-RT patch on linux 2.6.29.6. It runs on a MSI965GSE
industial board with Intel ATOM CPU (N270, 1,6GHz) and i945GSE Northbridge.
I got about 45µs as maximum and 13µs as average latency when hyperthreading is
disabled. With enabled Hyperthreading the maximum latency increses to about
100µs. I measured the latency with cyclictest.
What can i do to get better maximum latency? Can I do somthing in the kernel
configuration or are there some kernel bootoptions? Or is it still impossible
with this CPU to get better results?
Thanks in advance,
Max Miller
Make sure you turn off any power management settings in the BIOS and
turn off the irqbalance and cpuspeed services on the Linux side.
What cyclictest command are you using to measure latency?
Clark
I run cyclictest as follows:
cyclictest -n -t3 -p99
For generating additional system load i run (one to several instances):
while true; do echo "blah" > /dev/null; done &
Then i watch the max. latency from the thread with the highest priority.
Sometimes i add the parameter '-h' to generate a history. In this
history i can
see that the most latency times are under 20µs, only about 5ppm are
worse than 30µs.
Am i doing this correctly?
The only powersave setting in the BIOS is "Intel speedstep" which i
disabled.
I will check with disabled "irqbalance and cpuspeed services" disabled
and will report later.
What should the adequate max. latency on this system?
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