Messages in this thread | | | Date | Fri, 25 Dec 2009 09:35:04 +0100 | From | Arjan van de Ven <> | Subject | Re: [PATCH] prctl: return MCE process flags through pointer |
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On Wed, 23 Dec 2009 10:54:50 -0800 Andrew Morton <akpm@linux-foundation.org> wrote:
> On Wed, 23 Dec 2009 09:56:04 -0800 "Smith, GeoffX" > <geoffx.smith@intel.com> wrote: > > > >Why are task_struct.timer_slack_ns and > > >task_struct.default_timer_slack_ns unsigned long, btw? AFACIT we > > >could make them unsigned ints. > > > > Timer slack is not a Boolean or enum, and we want the greatest > > range possible. (Actually, I'd like to talk Arjan into using the > > same time structure as select(), but that's another discussion.) > > Internally hrtimer uses unsigned long. I know long and unsigned > > long are the same on some architectures, but let's not introduce an > > unnatural restriction -- recall that arg2 is unsigned long. > > Using unsigned ints will reduce the size of the task_struct. > > Is there any conceivable case for a timer_slack which exceeds four > seconds?
the largest I've seen asked in practice is 2 seconds. But even at 100 msec or more you're talking about very special applications; rounding up timers otherwise really impacts the functionality of the app in a bad way.
> If so, what is it, and if so, why this: > > #define MAX_SLACK (100 * NSEC_PER_MSEC)
this is the max for "automatic slack"
-- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org
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