On 05.09.2005 [22:55:01 +0530], Srivatsa Vaddagiri wrote: > On Mon, Sep 05, 2005 at 09:57:30AM -0700, Nishanth Aravamudan wrote: > > I think it's ok where it is. Currently, with x86, at least, you can have > > an independent interrupt source and time source (not true for all archs, > > of course, ppc64 being a good example, I think?) Perhaps "handler" > > By "independent" do you mean driven by separate clocks? PPC64 does > use decrementer as its interrupt source and Time-base-register as > its timesource AFAIK. Both are driven by the same clock I think.
Well, independent as in not the same, I meant. Let me think about it and look at the code a bit, before making myself or anyone else more confused. John, do you have any input on what I'm getting at? I know we have discussed this before... > > What may be useful is something similar to what John Stultz does in his > > rework, attaching priorities to the various interrupt sources. For > > example, on x86, if we have an HPET, then we should use it, if not, then > > use APIC and PIT, but if the APIC doesn't exist in h/w, or is buggy > > (perhaps determined via a calibration loop), then only use the PIT. > > This logic is what the arch-code should follow in picking its interrupt > source and is independent of dyn-tick. dyn-tick just works with whatever > arch-code has chosen as its interrupt source. Yes, true. I didn't mean for the h/w interrupt source selection to be part of the arch-independent code, but that we might need to include a priority field in the interrupt_source structure to allow the arch-dependent code to do so. > > I agree. I guess max_skip, to me, is what the kernel thinks the > > interrupt source should maximally skip by, not what the interrupt source > > thinks it can do. So, I think it fits in fine with what you are saying > > and with the code you have in the current patch. > > Great! > > > I was just wondering; I guess it makes sense, but did you check to see > > if it ever *doesn't* get called? Like I said, __run_timers() [from how I > > Haven't tested that, but I feel can happen in practice, since we dont > control device interrupts. Well, it would be interesting to see if there's any difference without that function, or if it's even getting called. > > base->timer_jiffies) [the condition in run_timer_softirq()] is not. How > > much does it cost to raise the softirq, if it is going to return > > immediately from the callback? > > Don't know. It just felt nice to avoid any unnecessary invocations. Yes, but it also might add a function which doesn't need to be. I'll take a closer look at this too. Thanks, Nish - 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/
