Re: Workaround for wrapping loadaverage

From: Con Kolivas
Date: Wed Nov 10 2004 - 05:01:53 EST

Herbert Poetzl wrote:
On Wed, Nov 10, 2004 at 08:49:41AM +1100, Con Kolivas wrote:

Herbert Poetzl wrote:

but I agree that a higher resolution would be a good
idea ... also doing the calculation when the number
of running/uninterruptible processes has changed would
be a good idea ...

This could get very expensive. A modern cpu can do about 700,000 context switches per second of a real task with the current linux kernel so I'd suggest not doing this.

hmm, right it can, do you have any stats about the
'typical' workload behaviour?

How long is a piece of string? It depends entirely on your workload. On a desktop machine just switching applications pushes it to 10,000. Basically you end up making it an O(n) calculation by increasing the overhead of it (albeit small) proportionately to the context switch load which is usually significantly higher than the system load.

do you know the average time between changes of nr_running and nr_uninterruptible?

Same answer. Depends entirely on the workload and to whether your running tasks sleep at all or not (hint - most do). While it will be a lower number than the number of context switches, it potentially can be as high with just the right sort of threads (think server, network type stuff).



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