From mboxrd@z Thu Jan  1 00:00:00 1970
Date: Fri,  1 Jul 2011 16:00:26 +0200
From: Henning Schild <henning@plan9.bell-labs.com>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
Message-ID: <20110701160026.0db036cd@leffe.cs.bell-labs.com>
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Subject: [9fans] why not halt in x86 multicore
Topicbox-Message-UUID: f8dcbd88-ead6-11e9-9d60-3106f5b1d025

Hi,

in pc/main.c idlehands() the kernel decides to release the CPU only
when you are not running a multicore kernel. As a result there is only
busy waiting. Unfortunately there is no hint telling why we do not let
the CPU rest a little.

> void
> idlehands(void)
> {
> 	if(conf.nmach == 1)
> 		halt();
> }

I am running a mostly idle plan9 VM on my laptop and it causes the
battery to discharge in no time. Right now my kernel has the condition
commented out and it seems to work fine. Still i would like
to understand why this condition was put there. It is probably causing a
lot of energy to be wasted which should better be for a good reason.

Henning