Messages in this thread |  | | From | John Alvord <> | | Subject | Re: [2.4.17/18pre] VM and swap - it's really unusable | | Date | Tue, 08 Jan 2002 16:29:59 -0800 |
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On Wed, 9 Jan 2002 00:10:38 +0000 (GMT), Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
>> Preemptive gives better interactivity under load, which is the whole >> point of multitasking (think about it). If you don't want the overhead >> (which also exists without preemptive) run #processes == #processors. > >That is generally not true. Pe-emption is used in user space to prevent >applications doing very stupid things. Pre-emption in a trusted environment >can often be most efficient if done by the programs themselves. > >Userspace is not a trusted environment The best part about planned preemption points is that there is minimal state to save when an interruption occurs.
> >> I'm really surprised that people are still actually arguing _against_ >> preemptive multitasking in this day and age. This is a no-brainer in >> the long run, where current corner cases aren't holding us back. > >Andrew's patches give you 1mS worst case latency for normal situations, that >is below human perception, and below scheduling granularity. In other words >without the efficiency loss and the debugging problems you can place the >far enough latency below other effects that it isnt worth attacking any more.
Incidently human visual perception runs around 200 milliseconds minimum and hearing/touch perception around 100 milliseconds if the signal has to go through the brain. Of course we extend our perceptions with tools/programs etc.
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