Messages in this thread | | | From | Mark Salisbury <> | Subject | Re: No 100 HZ timer ! | Date | Tue, 10 Apr 2001 08:27:13 -0400 |
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On Tue, 10 Apr 2001, Alan Cox wrote: > > 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. > > Measure the number of clocks executing a timer interrupt. rdtsc is fast. Now > consider the fact that out of this you get KHz or better scheduling > resolution required for games and midi. I'd say it looks good. I agree > the accounting of user/system time needs care to avoid slowing down syscall > paths > > Alan
the system I implemented this in went from 25 Millisecond resolution to 25-60 Nanosecond resolution (depending on the CPU underneath). that is a theoretical factor of 500,000 to 1,000,000 improvement in resolution for timed events, and the clock overhead after the change was about the same. (+-10% depending on underlying CPU)
this is on a system that only had one clock tick per process quantum, as opposed to the 10 in linux.
-- /*------------------------------------------------** ** Mark Salisbury | Mercury Computer Systems ** ** mbs@mc.com | System OS - Kernel Team ** **------------------------------------------------** ** I will be riding in the Multiple Sclerosis ** ** Great Mass Getaway, a 150 mile bike ride from ** ** Boston to Provincetown. Last year I raised ** ** over $1200. This year I would like to beat ** ** that. If you would like to contribute, ** ** please contact me. ** **------------------------------------------------*/
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