# tickless timer question

## mrpringle

In my kernel config I have the tickless timer option selected and also high resolution timer support. Then under the Timer frequency option 250Hz is selected by default. I just have a few questions about these options.

If the tickless timer option is chosen, does that mean the timer frequency has no meaning?

If dynamic ticks is enabled what exactly is my timer resolution?

Lastly

what exactly does high resolution timer support do, and does it still work if I have a tickless timer?

----------

## Naib

The kernel has an internal "tick" which is used for it todo stuff (schedular tick).

A higher timer (1000hz > 250Hz) means that you may gain a more responsive system (or you may get a drop in performance... all depends on what you are doing).

A higher tick means the kernel is woken up more often, a woken kernel uses more power 

tickless setting just means the kernel can operate at two ticks. 

1) what the kernel setting is

2) no wakeup

eg if you are doing alot of things then the tick will set a wakup for every 1ms (@1khz), but say your PC load suddenly dropped off (you went to make a coffee and essencially yr machine was idling). with a tick'ed system every 1ms the kernel would be woken up EVEN if there was nothing todo. In a tickless system the kernel knows when to wake up, such a wakeup cannot be faster then 1ms, but it can be alot longer. This produces energy savings

----------

## mrpringle

Thanks for the explanation but I still have some questions about how the options interact with each other.

If I enable High resolution timer support, does this mean the timer frequency setting doesn't have any affect on the tick rate? For example will enabling high res timer support and setting the timer frequency to 1000MHz give me better resolution than enabling high res timer support and setting the timer frequency to 250Hz?

I don't think this is at all explained in the configuration.

----------

