On 06/28/2012 01:21 PM, solmac john wrote:
> Thanks for reply
> what is CONFIG_NO_HZ
Hi!
If you have no idea what a config entry means, use the help in
menuconfig (or whatever you are using)... e.g. for CONFIG_NO_HZ tells you
----------<snip>--------------
CONFIG_NO_HZ:
This option enables a tickless system: timer interrupts will
only trigger on an as-needed basis both when the system is
busy and when the system is idle.
Symbol: NO_HZ [=n]
Type : boolean
Prompt: Tickless System (Dynamic Ticks)
Defined at kernel/time/Kconfig:7
Depends on: !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS [=y]
Location:
-> Processor type and features
Selects: TICK_ONESHOT [=n]
----------<snap>-------------
So this already gives you a general idea what the config entry does, and
some other useful info like dependency on other stuff that has to be
turn on/off.
> can we enable CONFIG_NO_HZ and CONFIG_HZ both in our config
This question is also answered here, as "Depends on:" would include
!CONFIG_HZ_250 if it had to be switched or sth.
> and what the drawback of dynamic CONFIG_NO_HZ tick.
I think the problems of longer latencies only apply on idle systems. Not
100% sure, but I think when the cpu goes into idle, the periodic timer
is stopped and longer intervals are done using one-shot timer to avoid
forcing the cpu out of idle just to see that nothing is to do and go
back into idle.
But I think if the CPU is not in idle the periodic timer.
regards,
andi
>
>
> On Tue, Jun 26, 2012 at 10:47 AM, Mulyadi Santosa
> <mulyadi.santosa@xxxxxxxxx <mailto:mulyadi.santosa@xxxxxxxxx>> wrote:
>
> Hi... :)
>
> On Tue, Jun 26, 2012 at 12:10 PM, solmac john
> <johnsolmac@xxxxxxxxx <mailto:johnsolmac@xxxxxxxxx>> wrote:
> > I am using ARM multicore board and by default
>
> okay, I am answering it from what I know about HZ impact on x86...
>
> > CONFIG_HZ=250
>
> looks good... a middle safe number, not too high not too low...
>
> > Query: - 1- How to decide HZ for particular hardware
>
> it's you who decide...do you want finer grained timer? or coarse one?
>
> the impact is usually toward latency and responsiveness....together
> with preemption model you choose actually.
>
> > 2- Which is the best open source tool to test system
> > performance from given HZ.
>
> run your application in that platform and see if it gives you impact.
> from my experience, unless you need application that is sensitive in
> timing such as MIDI sequencer, you won't notice the difference.
>
> --
> regards,
>
> Mulyadi Santosa
> Freelance Linux trainer and consultant
>
> blog: the-hydra.blogspot.com <http://the-hydra.blogspot.com/>
> training: mulyaditraining.blogspot.com
> <http://mulyaditraining.blogspot.com/>
>
>
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies@xxxxxxxxxxxxxxxxx
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>
_______________________________________________
Kernelnewbies mailing list
Kernelnewbies@xxxxxxxxxxxxxxxxx
http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
