Re: [PATCH] scheduler patch, faster still

Rik van Riel (H.H.vanRiel@phys.uu.nl)
Tue, 29 Sep 1998 00:14:47 +0200 (CEST)


On Mon, 28 Sep 1998, MOLNAR Ingo wrote:
> On Mon, 28 Sep 1998 yodaiken@chelm.cs.nmt.edu wrote:
>
> > Is it? And, isn't Richard arguing that his change makes sense only for
> > long queues?
>
> aggreed. 'long runqueues' are definitely a red herring. Very big (Linux)
> servers and even artificial 'exploit' programs could not show any RL case
> where there are long runqueues. Eg. someone at Kiva (now they are
> Netscape) has asked the same questions and has run statistics on a very
> big webserver and the average runqueue length was around 3, maxing out at
> 15.

OK. This is a valid point against Richard's proposed changes.

> Long runqueues might be a problem on other OSs, but not on Linux. (or if
> yes, please show me the case)
> (barring one case, when there are alot of CPU-bound processes around, in
> which case those processes waste so much cache resources anyway)

That's OK, since they still run their full timeslice
before having their priority restored. Two CPU-bound
tasks thrash the cache just as much ast ten.

The problem with this is that interactive processes
also get their priority restored slower when there
are a lot of CPU-bound processes running. It seems
like that is fixed with my patch (which should be a
little more efficient, but I'd really like to keep
the slow-recharging for niced processes).

Knowing you, I think you might actually be interested
to take a look at my scheduler changes and make it
more efficient (it avoids the for_each_task() and adds
the cost in another place; it could probably be a little
faster).

Rik.
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