On Thursday 01 March 2007 22:33, Thomas Gleixner wrote: > 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.
Oops I'm sorry if I made it sound like there's a dynticks problem. That was not my intent and I said as much in an earlier email. Even though I'm finding myself defending code that has already been softly tagged for redundancy, let's be clear here; we're talking about at most a further 70ms delay in scheduling a niced task in the presence of a nice 0 task, which is a reasonable delay for ksoftirqd which we nice the eyeballs out of in mainline. Considering under load our scheduler has been known to cause scheduling delays of 10 seconds I still don't see this as a bug. Dynticks just "points it out to us". -- -ck - 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/
