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Date: Mon, 05 Nov 2012 16:35:19 +0000
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To: Alexander Motin <mav@FreeBSD.org>
Subject: Re: Dynamic Ticks/HZ
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Cc: Davide Italiano <davide@freebsd.org>,
 FreeBSD Current <freebsd-current@freebsd.org>
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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.
> 
Hi,

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