Messages in this thread | | | Date | Thu, 11 Jul 2002 14:43:36 -0700 | From | george anzinger <> | Subject | Re: Periodic clock tick considered harmful (was: Re: HZ, preferably as |
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Alan Cox wrote: > > > First blush is HELL YES! The issue is accounting. When you > > ask how long a program ran, you are looking at the > > accounting that happens on a tick. This is where one of two > > Thats also an implementation issue. Note that the current code is also > wildly inaccurate. Mr Shannon says we are good to at best 50 run/sleep > changes a second. I've got "100% busy" workloads that are 99% asleep. > > Tracking cpu usage at task switch works a lot better for newer processors > which as well as having rdtsc also have performance counters. In fact you > can do much more interesting things on modern PC class platforms like > scheduling using pre-emption interrupts based on instructions executed, > memory accesses and more. > Oh, I agree. Hardware could make all this a lot easier. -- George Anzinger george@mvista.com High-res-timers: http://sourceforge.net/projects/high-res-timers/ Real time sched: http://sourceforge.net/projects/rtsched/ Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml - 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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