Messages in this thread | | | Subject | Re: sched_clock() uses are broken | From | Mike Galbraith <> | Date | Wed, 03 May 2006 11:31:38 +0200 |
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On Wed, 2006-05-03 at 11:16 +0200, Andi Kleen wrote: > On Wednesday 03 May 2006 11:11, Mike Galbraith wrote: > > On Wed, 2006-05-03 at 09:40 +0200, Andi Kleen wrote: > > > On Wednesday 03 May 2006 09:09, Mike Galbraith wrote: > > > > > > > Given that most people are going to end up using the pm_timer anyway, I > > > > don't see the point of even having a sched_clock(). If it's jiffy > > > > resolution, it's useless. If it's wildly inaccurate (as it is in the > > > > SMP case, monotonicity issues aside) it's more than useless. > > > > > > For sched_clock TSC is always used and it's fine - sched_clock > > > doesn't require the guarantees that make TSC often useless otherwise > > > > Regrettable, that's not true. > > Hmm, maybe I'm thinking too much x86-64. At least on x86-64 it's true. > > I don't see a big reason to not do this on i386 either, except > on systems that truly don't have a TSC (386/486)
It should be this way on any system that has a half way functional high resolution source. Without it, the starvation scenario which sched_clock() was invented to solve returns. Making that the default wasn't (um um um) the most brilliant selection among available options.
> Ok i suppose if you don't want cruft you can always go to 64bit @)
Unemployed guys can't buy new toys without wives getting all grumpy ;-)
-Mike
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