High load w/ almost no CPU usage

[Brandon Allbery]

On Thu, Feb 5, 2015 at 12:45 PM, Matthew Grooms <mgrooms at shrew.net> wrote:

> But at seemingly random intervals, the load average jumps to a very high
> value, and then eventually drops back down to < 2.


One problem with using top to diagnose this kind of thing is that you can
have processes that have very short activation periods, which won't show up
much in top because they don't run for long enough to collect much CPU time
or indeed to produce user-noticeable load, but will drive the apparent load
up because they're on the run queue so much. dtrace probes might be more
helpful here.

Also you might want to look at interrupts (e.g. monitor "vmstat -i" output,
then again move to dtrace for finer grained monitoring).

-- 
brandon s allbery kf8nh                               sine nomine associates
allbery.b at gmail.com                                  ballbery at sinenomine.net
unix, openafs, kerberos, infrastructure, xmonad        http://sinenomine.net