Initial 6.1 questions

Danial Thom danial_thom at
Tue Jun 13 18:43:40 UTC 2006

--- Robert Watson <rwatson at> wrote:

> On Tue, 13 Jun 2006, Danial Thom wrote:
> > Maybe someone can explain this output. The
> top line shows 99.6%idle. Is it 
> > just showing CPU 0s stats on the top line?
> Two types of measurements are taken: sampled
> ticks regarding whether the 
> system as a while is in {user, nice, system,
> intr, idle}, and then sampling 
> for individual processes.  Right now, the
> system measurements are kept in a 
> simple array of tick counters called cp_time. 
> John Baldwin and others have 
> changes that make these tick counters per-CPU. 
> The lines at the top of 
> top(1)'s output are derived from those tick
> counters.  Ticks are measured on 
> each CPU, so those are a summary across all
> CPUs.  To add cpustat support, we 
> need to merge John's patch to make cp_time
> per-CPU (ie., different counters 
> for different CPUs) and teach the userland
> tools to retrieve them.  When you 
> run top you'll notice that it adjusts the
> measurements each refresh.  In 
> effect, what it's doing is sampling the change
> in tick counts over the window, 
> pulling down the new values and calculating the
> percentages of ticks in each 
> "bucket" in the last window.

That doesn't explain why the Top line shows 99.6%
idle, but the cpu idle threads are showing
significant usage. 

I'm getting a constant 6000 Interrupts / Second
on my em controller, yet top jumps all over the
place; sitting at 99% idle for 10 seconds, then
jumping to 50%, then somewhere in between. It
seems completely unreliable. The load I'm
applying is constant.


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