On Thu, Jan 15, 2009 at 09:44:42AM -0800, Andrew Morton wrote: > > Me too. Anecdotally, I haven't noticed this in my lab machines, but > > what I have noticed is on someone else's laptop (a hyperthreaded atom) > > that I was trying to demo powertop on was that IPI reschedule interrupts > > seem to be out of control ... they were ticking over at a really high > > rate and preventing the CPU from spending much time in the low C and P > > states. To me this implicates some scheduler problem since that's the > > primary producer of IPI reschedules ... I think it wouldn't be a > > significant extrapolation to predict that the scheduler might be the > > cause of the above problem as well. > > > > Good point. > > The context switch rate actually went down a bit. > > I wonder if the Intel test people have records of /proc/interrupts for > the various kernel versions. I think Chinang does, but he's out of office today. He did say in an earlier reply: > I took a quick look at the interrupts figure between 2.6.24 and 2.6.27. > i/o interuputs is slightly down in 2.6.27 (due to reduce throughput). > But both NMI and reschedule interrupt increased. Reschedule interrupts > is 2x of 2.6.24. So if the reschedule interrupt is happening twice as often, and the context switch rate is basically unchanged, I guess that means the scheduler is doing a lot more work to get approximately the same results. And that seems like a bad thing. Again, it's worth bearing in mind that these are all RT tasks, so the underlying problem may be very different from the one that both James and I have observed with an Atom laptop running predominantly non-RT tasks. -- Matthew Wilcox Intel Open Source Technology Centre "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step." -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
