Messages in this thread | | | From | Roger Larsson <> | Subject | Re: [2.4.17/18pre] VM and swap - it's really unusable | Date | Tue, 8 Jan 2002 23:00:59 +0100 |
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On Tuesdayen den 8 January 2002 21.13, Alan Cox wrote: > > low-latency kernel". Now, IF we can come to this decision, then > > internal preemption is the way to do it. But it affects ALL kernel > > The pre-empt patches just make things much much harder to debug. They > remove some of the predictability and the normal call chain following > goes out of the window because you end up seeing crashes in a thread with > no idea what ran the microsecond before > > Some of that happens now but this makes it vastly worse. > > The low latency patches don't change the basic predictability and > debuggability but allow you to hit a 1mS pre-empt target for the general > case. >
Yes, it does make things much much harder to debug - but: * If you get a problem on a preemtive UP kernel, it is likely to be a problem on a SMP too - and those are hard to debug aswell. But the positive aspect is that you get more people that can do the debugging... :-) (One CPU gets delayed with handling a IRQ the other runs into the critical section) * It is optional at compile time. And could even be made run time optional / CPU ! Just set a too big value on the counter and it will never reschedule...
/RogerL
-- Roger Larsson Skellefteå Sweden - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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