Strange happening

Adam Moffett adamlists at
Wed Jul 17 17:05:55 UTC 2013

I just had a moment that made me feel like the stupidest man on the planet.

I restarted ISC  dhcpd and it didn't seem to be working.  The log 
indicated that it had started, and tcpdump indicated that we were 
receiving requests.  I started it in debug mode and the console sat 
there doing nothing.

I looked at top and observed the CPU was about 89% waiting and 0% idle.  
After some time passed (I wasn't counting) suddenly the console session 
with dhcpd running in debug mode started scrolling along like mad.  I 
checked top again and now we're 0% waiting.

I assume the system was I/O bound so I guess this is not strictly 
related to dhcpd, so flag me off topic and flame me if you want, but if 
it happens again I'm wondering if there's a way to determine what 
processes are waiting for I/O and/or what they're waiting for specifically.

This system doesn't really do much besides DHCP so I'm a little stunned 
that this happened.

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