F-ckin Leap Seconds, how do they work?

Matthew Palmer mpalmer at hezmatt.org
Tue Jul 3 07:27:14 UTC 2012


On Mon, Jul 02, 2012 at 09:13:42AM -0700, Michael Thomas wrote:
> My centos 6/64 running 3.0 seemed to weather it too. I'm not quite
> clear on what I should be looking for to classify it as being "broken" though.

The problems I saw were related to programs that use futex(2) (Java, MySQL,
Chromium, in my personal experience) chewing up lots of CPU because the
futex system call wasn't quite doing what it was supposed to be doing
(waking up threads when they were OK to proceed) and instead constantly
waking the threads up, having the threads go "OK, so my lock is clear and
I'm ready to go?", the kernel saying "oh, no, sorry" and the thread going
back to sleep again -- only to be woken up again immediately.  Sort of an
object lesson in why busy-wait locks suck.

- Matt

-- 
The main advantages of Haynes and Chilton manuals are that they cost $15,
where the factory manuals cost $100 and up, and that they will tell you how
to use two hammers, a block of wood, and a meerkat to replace "special tool
no. 2-112-A"	-- Matt Roberds in asr.





More information about the NANOG mailing list