Hi all/jim,
On 9/17/06, Jim Cromie <jim.cromie@xxxxxxxxx> wrote:
Tharindu Rukshan Bamunuarachchi wrote:
> Hi all,
>
> What is the best method of improving the real time behaviour of an
> application.
>
'best' needs more elaboration.
- what constraints ?
We have trading system with 4-7 hops connected in a loop. When a
network packet reach each host, we need minimum latecey to wake up
application and do the processing. Processin time is very samll and
usually takes around 50-60microseconds.
I have tested this with two HZ values;
1. 1000 set to HZ
2. 1500 set to HZ
for 1000HZ i got around 2000 microsecond latencey in best case
for 1500HZ i got around 1300 microsecond latencey in best case
old / new kernels ?
This new 2.6.9 kernel (Actually RHEL 4 update 2)
keeping old apps ?
We have minimized other appllications. Only application per host.
how hard/soft is your RT reqs ?
I think we need soft RT
CONFIG_PREEMPT_RT is in recent mainline, as is PREEMPT_VOLUNTARY
I have settled PREEMPT_RT option
then theres the -rt tree, and xenomai.org for a co-kernel approach.
> I can see two approaches
>
you seem to limit your consideration to main-line kernels.
> 1) setting the scheduling class & priority (chrt & nice)
>
> 2) setting of kernel parameters ( The option 1 is not available, bcos
> of app is not allowed to adjust its scheduling attributes)
>
> We have already set HZ =1000.
>
> Can we reduce the default time slice to 10ms or 20 ms without any side
> effects.
I think for 1000 HZ default timeslice is around 100ms; ( i may be wrong ;)
whats the default timeslice ?
loss of thruput is a side effect, and cutting slice 10-fold is bound to
increase context switches.
--
Tharindu Rukshan Bamunuarachchi
all fabrications are subject to decay
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