getting 'load averages' (or something similar) from inside a _kernel_
bonomi at mail.r-bonomi.com
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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