getting 'load averages' (or something similar) from inside a _kernel_

Robert Bonomi bonomi at
Mon Dec 15 22:58:38 UTC 2014

  I'm trying to get the current 'runnable processes' count from inside a 
kernel loadable module for BSD 8.4, so I can tweak it's behavior depending
on the current activity level.  All I've found so far is what's in 'man 9 
runqueue', and it is *badly* out-of-sync with the 8.4 kernel code. <snarl>
<wry grin>   e.g., the external arrays at the beginning of the synopisis
are shown as being of type 'struct rq' -- but there *ISN"T* any defined 
struct 'rq'; it seems to be named 'runq', at least in /usr/include/sys/runq.h

Then the cr*p gets deeper -- trying to make heads or tails out of how to
get a count of runnable processes from the _arrays_ (of unknown size) 
described on the 'man 9 runqueue' page info has me defeated. 
Looking at '/usr/include/sys/runq.h', it appears that 'struct runq' is
a single item with an array of queues (by 'nice' level), and a bitmap of
which array elements have non-zero length queues.

I'm perfectly willing to brute-force the data out of the queue lists, *IF*
there's some reasonable, _current_, descriptive info of the format/usage
of those kernel structures.

Alternatively, is there a way to directly access the 'sysctl' MIB data in
kernel memory.  sysctl(3) is out -- it's in 'libc', and not available to 
kernel modules.  Pointers to descriptions of the kernel in-memory data for
that MIB would be a big help.   Or 'where to ask', if there's a better place.

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