Date: Fri, 3 Mar 2006 21:40:02 -0800
From: "Randy.Dunlap" <rdunlap@xenotime.net>
To: Mike Galbraith <efault@gmx.de>
Cc: kernel@kolivas.org, pwil3058@bigpond.net.au, linux-kernel@vger.kernel.org,
       mingo@elte.hu, nickpiggin@yahoo.com.au, kenneth.w.chen@intel.com,
       akpm@osdl.org
Subject: Re: [patch 2.6.16-rc5-mm2]  sched_cleanup-V17 - task throttling
 patch 1 of 2
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On Sat, 04 Mar 2006 06:29:47 +0100 Mike Galbraith wrote:

> On Sat, 2006-03-04 at 16:24 +1100, Con Kolivas wrote:
> > On Saturday 04 March 2006 16:20, Mike Galbraith wrote:
> > > On Sat, 2006-03-04 at 13:33 +1100, Peter Williams wrote:
> > > > >  include/linux/sched.h |    3 -
> > > > >  kernel/sched.c        |  136
> > > > > +++++++++++++++++++++++++++++--------------------- 2 files changed, 82
> > > > > insertions(+), 57 deletions(-)
> > > > >
> > > > > --- linux-2.6.16-rc5-mm2/include/linux/sched.h.org	2006-03-01
> > > > > 15:06:22.000000000 +0100 +++
> > > > > linux-2.6.16-rc5-mm2/include/linux/sched.h	2006-03-02
> > > > > 08:33:12.000000000 +0100 @@ -720,7 +720,8 @@
> > > > >
> > > > >  	unsigned long policy;
> > > > >  	cpumask_t cpus_allowed;
> > > > > -	unsigned int time_slice, first_time_slice;
> > > > > +	int time_slice;
> > > >
> > > > Can you guarantee that int is big enough to hold a time slice in
> > > > nanoseconds on all systems?  I think that you'll need more than 16 bits.
> > >
> > > Nope, that's a big fat bug.
> > 
> > Most ints are 32bit anyway, but even a 32 bit unsigned int overflows with 
> > nanoseconds at 4.2 seconds. A signed one at about half that. Our timeslices 
> > are never that large, but then int isn't always 32bit either.
> 
> Yup.  I just didn't realize that there were 16 bit integers out there.

LDD 3rd ed. doesn't know about them either.  Same for me.

---
~Randy
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