Messages in this thread | | | Date | Sat, 29 Dec 2001 14:24:27 -0800 (PST) | From | Davide Libenzi <> | Subject | Re: [RFC] Scheduler issue 1, RT tasks ... |
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On Sat, 29 Dec 2001, Dieter [iso-8859-15] Nützel wrote:
> Martin Knoblauch wrote: > > > > > Re: [RFC] Scheduler issue 1, RT tasks ... > > > > > > > > > > > Right, that was my question. George says, in your words, "for better > > > > > > > standards compliancy ..." and I want to know why you guys think > > > that. > > > > > > The thought was that if someone need RT tasks he probably need a very > > > low latency and so the idea that by applying global preemption decisions > > > would lead to a better compliancy. But i'll be happy to ear that this is > > > false anyway ... > > > > > > > without wanting to start a RT flame-fest, what do people really want > > when they talk about RT in this [Linux] context: > > > > - very low latency > > - deterministic latency ("never to exceed") > > - both > > - something completely different > > > > All of the above from time to time and user to user. That is, some > > folks want one or more of the above, some folks want more, some less. > > What is really up? Well they have a job to do that requires certain > > things. Different jobs require different capabilities. It is hard to > > say that any given system will do a reasonably complex job with out > > testing. For example we may have the required latency but find the > > system fails because, to get the latency, we preempted another task that > > was (and so still is) in the middle of updating something we need to > > complete the job. > > So George what direction should I try for some tests? > 2.4.17 plus your and Robert's preempt plus lock-break? > Add your high-res-timers, rtscheduler or both? > Do they apply against 2.4.17/2.4.18-pre1? > A combination of the above plus Davide's BMQS? > > I ask because my MP3/Ogg-Vorbis hiccup during dbench isn't solved anyway. > Running 2.4.17 + preempt + lock-break + 10_vm-21 (AA). > Some wisdom?
A bad scheduler can make the latency to increase but in your case i don't think that it could increase that much ( in percent ). By copying a huge file arund you can experience spots of 1-2 secs of machine freeze and this is definitely not the scheduler. The demage the a bad scheduler can do is directly proportional to the cs anyway.
- Davide
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