Re: [Announce] [patch] Modular Scheduler Core and Completely Fair Scheduler [CFS]

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Matt Mackall wrote:
On Wed, Apr 18, 2007 at 08:37:11AM +0200, Nick Piggin wrote:

[2] It's trivial to construct two or more perfectly reasonable and
desirable definitions of fairness that are mutually incompatible.
Probably not if you use common sense, and in the context of a replacement
for the 2.6 scheduler.

Ok, trivial example. You cannot allocate equal CPU time to
processes/tasks and simultaneously allocate equal time to thread
groups. Is it common sense that a heavily-threaded app should be able
to get hugely more CPU than a well-written app? No. I don't want Joe's
stupid Java app to make my compile crawl.

On the other hand, if my heavily threaded app is, say, a voicemail
server serving 30 customers, I probably want it to get 30x the CPU of
my gzip job.

Matt, you tickled a thought... on one hand we have a single user running a threaded application, and it ideally should get the same total CPU as a user running a single thread process. On the other hand we have a threaded application, call it sendmail, nnrpd, httpd, bind, whatever. In that case each thread is really providing service for an independent user, and should get an appropriate share of the CPU.

Perhaps the solution is to add a means for identifying server processes, by capability, or by membership in a "server" group, or by having the initiating process set some flag at exec() time. That doesn't necessarily solve problems, but it may provide more information to allow them to be soluble.

--
Bill Davidsen <[email protected]>
  "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot
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