Messages in this thread | | | From | Marin Mitov <> | Subject | Re: some thoughts about TSC based delay_tsc() | Date | Wed, 21 Nov 2007 22:06:34 +0200 |
| |
On Wednesday 21 November 2007 09:27:54 pm you wrote: > * Marin Mitov <mitov@issp.bas.bg> wrote: > > Hi Ingo, > > > > The patch is quite good ;-) but we forget when it is needed :-( In > > fact we need it only for PREEMPT SMP kernels - it could hurt PREEMPT > > UP kernels (no migration possible), so no need for > > preempt_disable()/preempt_enable(). > > > > In short the old version of delay_tsc() is good for UP kernels and NON > > PREEMPT SMP kernels too. > > please reply to the public list, so that discussions do not get lost. > > i dont think there's any problem: udelay() is about _wasting_ cycles - > it's what drivers use for short delays.
Sure for the thread executing udelay(), but not for the other ready threads which should also wait till preempt_enable() to grab the same cpu even for PREEMPT (UP or SMP) kernels (or I misunderstand something?).
Marin > > Ingo
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |