Re: 2.6.21-rc1: known regressions (v2) (part 2)

Thomas Gleixner
2007-03-01T11:28:17Z

On Thu, 2007-03-01 at 22:13 +1100, Con Kolivas wrote:
> > if then there should be a mechanism /in the hardware/ to set the
> > priority of a CPU - and then the hardware could decide how to prioritize
> > between siblings. Doing this in software is really hard.
>
> And that's the depressing part because of course I was interested in that as
> the original approach to the problem (and it was a big problem). When I spoke
> to Intel and AMD (of course to date no SMT AMD chip exists) at kernel summit
> they said it was too hard to implement hardware priorities well. Which is
> real odd since IBM have already done it with Power...
>
> Still I think it has been working fine in software till now, but now it has to
> deal with the added confusion of dynticks, so I already know what will happen
> to it.

Well, it's not a dyntick problem in the first place. Even w/o dynticks
we go idle with local_softirq_pending(). Dynticks contains an explicit
check for that, which makes it visible.

tglx