Re: cyclictest better values with system load than without (OMAP3530 target)

[Stefan Roese <stefan.roese@gmail.com>]

Hi Dmitry!

On 26.11.2013 15:21, Dmitry Lysenko wrote:
> On Marvell Kirkwood at 1.2Ghz and 3.2.51-rt72 kernel I have slightly
> better results:
> 
> --- with hackbench:
> 
> root@debian:~/rt-tests# ./cyclictest -l 10000 -i 1000 -n -p 80 -q
> T: 0 (10268) P:80 I:1000 C:  10000 Min:     16 Act:   29 Avg:   29 Max:      46
> 
> --- w/o hackbench:
> 
> root@debian:~/rt-tests# ./cyclictest -l 10000 -i 1000 -n -p 80 -q
> T: 0 (12686) P:80 I:1000 C:  10000 Min:      5 Act:    6 Avg:    6 Max:      22
> 
> -- .config:
> CONFIG_TICK_ONESHOT=y
> # CONFIG_NO_HZ is not set
> CONFIG_HIGH_RES_TIMERS=y
> 
> # CONFIG_CPU_IDLE is not set
> 
> Try to play with:
> 
> # CONFIG_PM_RUNTIME is not set
> # CONFIG_ARM_CPU_SUSPEND is not set

Thanks, this was helpful. After some tweaks I was able to disable
CONFIG_PM_RUNTIME and ARM_CPU_SUSPEND. And after disabling NO_HZ and
less CONFIG_DEBUG_xxx options I now have the following results:

Idle:
# ./cyclictest -l 10000 -i 1000 -n -p 80 -q
# /dev/cpu_dma_latency set to 0us
T: 0 ( 1382) P:80 I:1000 C:  10000 Min:     12 Act:  141 Avg:  127 Max:     202

Load:
# ./cyclictest -l 10000 -i 1000 -n -p 80 -q
# /dev/cpu_dma_latency set to 0us
T: 0 ( 2777) P:80 I:1000 C:  10000 Min:     26 Act:  167 Avg:  152 Max:     229

So the test now finally has better results on a idle system than on
one with heavy system load. The numbers are still far away from your
latency values on the 1.2GHz Kirkwood. Does anybody have OMAP3
values at hand to compare?

Thanks for your input,
Stefan