Messages in this thread | | | Date | Tue, 24 Oct 2000 15:48:11 -0500 (CDT) | From | Oliver Xymoron <> | Subject | Re: PC speaker driver patch for 2.4.0-test10-pre3 |
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On Tue, 24 Oct 2000, Pavel Machek wrote:
> Hi! > > > > oxymoron@waste.org said: > > > > You can also pretty trivially keep track of an error term so that the > > > > clock is right on average: > > > > > > True, but I don't want 'right on average'. I want 'not screwed with at all'. > > > Shifting the timer tick onto the RTC will give me that. > > > > > > Even if we _do_ get the maths right, fudging with the frequency of the > > > system timer is still an ugly hack. > > > > I personally think the system timer is already an ugly hack. HZ is > > arbitrary, slow by modern standards, and introduces latency. > > As the comment you quoted points out, it's also not very accurate. > > Much better would be an agenda structure with one shot timers between > > events and jiffies based on cycle counters. This works on modern hardware > > and scales well for higher processor speeds. > > ...and breaks horribly when your CPU frequency changes... like on most > current notebooks.
The unit of time is arbitrary. Cycle counts just happens to be convenient on most machines and very high resolution. The important point is that hanging tasks off a periodic low-resolution timer is not scaling with CPU clock speeds at all and there are ways to throw it out.
-- "Love the dolphins," she advised him. "Write by W.A.S.T.E.."
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