Dynamic Ticks/HZ

Joe Holden lists at rewt.org.uk
Mon Nov 5 16:35:28 UTC 2012

Alexander Motin wrote:
> Hi.
> Full interrupt rate on some CPU means that your system is not idle, but 
> running some process. Another possibility is that you have DUMMYNET 
> compiled into your kernel, which tends to schedule callout for every HZ 
> tick, effectively blocking skipping interrupts for one of CPUs.
> Check 'top -SH' for running processes, or 'top -SH -m io -o vcsw' for 
> processes doing a lot of context switches. That most likely should give 
> an answer.

It looks like the device polling is what was causing it, once I'd 
removed that from kernconf it returned to normal - full interupt rate is 
ok though if I can increase the rate to a decent level

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