lilzz
Posts: 411
Joined: Sat Nov 30, 2013 5:27 pm

what's a kernel tick frequency?

Tue Feb 09, 2016 10:35 pm

kernel tick frequency (1000 Hz)t
which is 1kHz.

But the Broadcom Chipset for Pi is 900Mhz

What's the relationship between the two? Why kernek tick frequency is lower than chipset frequency.?

User avatar
lpsw
Posts: 157
Joined: Thu Jun 25, 2015 4:45 pm
Location: USA

Re: what's a kernel tick frequency?

Tue Feb 09, 2016 11:28 pm

IIRC the default timer interrupt frequency is 100Hz (not 1000Hz).
Google 'jiffies'.
Self-education is, I firmly believe, the only kind of education there is - Isaac Asimov

Heater
Posts: 13622
Joined: Tue Jul 17, 2012 3:02 pm

Re: what's a kernel tick frequency?

Tue Feb 09, 2016 11:36 pm

The kernel "tick" frequency is all about how often the kernel should check what process is running, what process wants to be running and what to do about it.

Clearly that must be a lot slower than the actual execution rate of instructions on the machine.

If the tick frequency is too low things don't get scheduled as promptly as you might like. That may cause problems with the user interface or with audio/video playing.

If the tick frequency is too fast, then you are spending too much time in the kernel code deciding what to do next. Over all performance of applications becomes slower.
Memory in C++ is a leaky abstraction .

gregeric
Posts: 1509
Joined: Mon Nov 28, 2011 10:08 am

Re: what's a kernel tick frequency?

Tue Feb 09, 2016 11:57 pm

There was some discussion on this recently over on https://github.com/raspberrypi/linux/issues/1216

Return to “General discussion”