On 10/08, Peter Zijlstra wrote: > > On Tue, Oct 07, 2014 at 09:50:46PM +0200, Oleg Nesterov wrote: > > And note that another caller of task_preempt_count(), set_cpu(), is > > fine but it doesn't really need this helper. > > > > And afaics we do not need ->saved_preempt_count at all, the trivial > > patch below makes it unnecessary, we can kill it and all its users. > > > > Not only this will simplify the code, this will make (well, almost) > > the per-cpu preempt counter arch-agnostic. > > > > Or I missed something? > > Two things, per-cpu isn't always faster on some archs, and load-store > archs have problems with PREEMPT_NEED_RESCHED, although arguably you can > do per-cpu preempt count without that.
Ah, but I didn't mean we should make it per-cpu on every arch. I meant that (imo) this change can cleanup x86 code, and it can also help if we want to change another arch to use per-cpu preempt_count. > > Do you think this makes sense? If yes, I'll try to make the patches. > > It penalizes everything but x86 I think. I don't think so. But please forget for the moment, lets discuss this later. Let me start with 2 simple preparations which imho make sense anyway. Then we will see. 1/2 looks like the obvious bugfix (iirc we already discussed this a bit), 2/2 depends on this patch. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
