Messages in this thread | | | Date | Sat, 9 Jan 1999 19:05:16 -0500 (EST) | From | "Richard B. Johnson" <> | Subject | Re: [PATCH] HZ change for ix86 |
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On Sat, 9 Jan 1999, Horvath Karoly wrote:
> On Fri, Jan 08, 1999 at 09:14:14AM -0500, Richard B. Johnson wrote: > > There seems to be a general misinformation about what the HZ value is. > > I will "simplicate and add lightness". > > still darkness here.... > > > However, if your code is doing: > > > > UncompressFonts(...........); > > ReadAudioFromDsp(...........); > > ConvolveImageData(..........); > > > > you don't want the CPU taken away until you are done. > > We can't prevent the kernel from taking away the CPU - and a higher HZ value > helps us get back the CPU as soon as possible.
If we don't do blocking system calls, we don't lose the CPU until our time-slice is up.
Once you lose the CPU, you may lose it for N time slices because there are N computable tasks that will get it before you get it back. This is a multitasking operating system with many more tasks than just yours. You get it CPU back when it's your turn, not the next timer-tick.
If N tasks are CPU bound, you sure want a long time-slice before the CPU gets stolen from you.
> > > doesn't produce visual effects. The higher the HZ value, the more > > often the CPU gets stolen from the interactive user. > > Why is that a problem? Here is an example: > You earn 1000$ a month. Your boss decides to pay you not monthly but weekly, > and you begin to complain that you only earn 250$.
Not accurate.
Cheers, Dick Johnson ***** FILE SYSTEM WAS MODIFIED ***** Penguin : Linux version 2.1.131 on an i686 machine (400.59 BogoMips). Warning : It's hard to remain at the trailing edge of technology. Wisdom : It's not a Y2K problem. It's a Y2Day problem.
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