Kill the power faster than poweroff?

Donald Becker becker at scyld.com
Fri Sep 12 09:54:17 EDT 2003


On Fri, 12 Sep 2003, Daniel Kidger wrote:

> For information, both flavours of Opteron that I have here have an
> out-of-band BMC that I can issue remote power-on/ power-off commands to over
> ethernet..

I'm a big fan of network IPMI 1.5, which is usually implemented by a
Baseboard Management Controller (BMC).  The BMC is a microcontroller
running on stand-by power.  It can control power, redirect the "serial"
console to the network, monitor temp/voltage/switches, configure the BIOS
and do a few other things.

The cleanest IPMI implementation uses an enhanced Ethernet controller
that redirects IPMI packets to the BMC instead of the OS.  This allows
installing a machine by plugging in only a power cord and Ethernet
cable.  Everything else may be done over the network.

But my understanding is that the issue here is the software shutdown
time.

The big culprit in the slow shutdown is the daemons.  We solved this
problem for cluster compute nodes in the Scyld system by developing a
unique system that does not require daemons.  Thus we can cleanly shut
down a slave node almost instantly.

But we want a standard, full-featured Linux installation as a cluster
master, and have the same slow shutdown issue there.  So why does a 3GHz
machine takes 10X more time to boot and shutdown than a slow machine
with an earlier Linux installation?  The biggest culprits are
  /etc/rc.d/init.d/functions
  /etc/rc.d/init.d/halt
which do explicit sleeps and have very poor scaling.  Fixing the
fundamental problems is difficult (you can just revert to an older
version), but it's easy to pick better numbers for the 'usleep' and
'sleep' calls.


-- 
Donald Becker				becker at scyld.com
Scyld Computing Corporation		http://www.scyld.com
914 Bay Ridge Road, Suite 220		Scyld Beowulf cluster system
Annapolis MD 21403			410-990-9993

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