Messages in this thread | | | Date | Tue, 10 Apr 2001 14:02:02 +0200 | From | Andi Kleen <> | Subject | Re: No 100 HZ timer ! |
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On Tue, Apr 10, 2001 at 12:18:03PM +0100, Alan Cox wrote: > > > interrupting decrementer. (i.e just about any modern chip) > > > > Just how would you do kernel/user CPU time accounting then ? It's currently done > > on every timer tick, and doing it less often would make it useless. > > On the contrary doing it less often but at the right time massively improves > its accuracy. You do it on reschedule. An rdtsc instruction is cheap and all > of a sudden you have nearly cycle accurate accounting
Does not sound very attractive all at all on non virtual machines (I see the point on UML/VM): making system entry/context switch/interrupts slower, making add_timer slower, just to process a few less timer interrupts. That's like robbing the fast paths for a slow path.
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