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SubjectRe: Linux 2.6.0-test6
Nick Piggin wrote:
> Rob Landley wrote:
>> On Sunday 28 September 2003 02:03, Con Kolivas wrote:
>>> On Sun, 28 Sep 2003 11:27, Linus Torvalds wrote:
>>>> from Andrew Morton. Most notably perhaps Con's scheduler changes that
>>>> have been discussed extensively and made it into the -mm tree for
>>>> testing.
>>> For those who are trying this for the first time, please note that the
>>> scheduler has been tuned to tell the difference between tasks of the
>>> _same_
>>> nice level. This means do NOT renice X or it will make audio skip unless
>>> you also renice your audio application by the same amount. Lots of
>>> distributions have done this for the old 2.4 scheduler which could not
>>> treat equal "nice" levels as differently as the new scheduler does
>>> and 2.6
>>> shouldn't need special treatment.
>>> So for testing note the following points:
>>> Make sure X is NOT reniced to -10 as many distributions are doing.
>>> Some shells spawn processes at nice +5 by default and this will make
>>> audio
>>> apps suffer.
>>> Make sure your hard disk, graphics card and audio card are performing at
>>> equal standard to your 2.4 kernel (ie dma is working, graphics is fully
>>> accelerated etc).
>> I.E. with your new scheduler, priority levels actually have enough of
>> an effect now that things that aren't reniced can be noticeably
>> starved by things that are.
> AFAIK, Con's scheduler doesn't change the nice implementation at all.
> Possibly some of his changes amplify its problems, or, more likely they
> remove most other scheduler problems leaving this one noticable.
> If X is running at -20, and xmms at +19, xmms is supposed to still get
> 5% of the CPU. Should be enough to run fine. Unfortunately this is
> achieved by giving X very large timeslices, so xmms's scheduling latency
> becomes large. The interactivity bonuses don't help, either.

there are 40 positions between -20 and 19, that doesn't equal 5% steps.
They don't even refer to % of cpu. If i nice a process to -20 it
doesn't get a given percentage of cpu just because it's -20. I may have
other processes at -20 as well. If you nice something to -20 and it is
actually using that cpu then things that are +19 shouldn't run and wont
run. If I nice -20 vmstat 1, it's not going to starve xmms (or any
better audio player). -20 means starve all and it should do that when
it actually makes use of the resources.

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