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Date: Wed, 4 Dec 2002 02:21:44 +0100
From: Andrea Arcangeli <andrea@suse.de>
To: Andrew Morton <akpm@digeo.com>
Cc: "Martin J. Bligh" <mbligh@aracnet.com>, Christoph Hellwig <hch@sgi.com>,
       rml@tech9.net, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] set_cpus_allowed() for 2.4
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On Tue, Dec 03, 2002 at 05:14:40PM -0800, Andrew Morton wrote:
> Andrea Arcangeli wrote:
> > 
> > On Tue, Dec 03, 2002 at 04:30:28PM -0800, Andrew Morton wrote:
> > > load is just one or more busywaits.  It has to be a compilation.  It
> > > could be something to do with all the short-lived processes, or gcc -pipe)
> > 
> > could be that we think they're very interactive or something like that.
> 
> I just retested.  This is on uniprocessor.  Running `make -j1 bzImage',
> while typing into a StarOffice 5.2 document:
> 
> - 2.4.19-pre4: smooth
> - 2.4.20aa1: Jerky.  Sometimes it's OK, sometimes a few characters
>   lag.
> 
> Then I disabled `-pipe' in the build and restarted it:
> 
> - 2.4.19-pre4: smooth
> - 2.4.20aa1: Quite a lot more jerky.  Enough to be a bit irritating.
> 
> > ...
> > >
> > > This problem is the "changed sched_yield semantics".  It was actually
> > > tested on uniprocessor.  The difference between 2.4 and 2.4-aa is
> > > still noticeable here, but it is not a terrible problem now.
> > 
> > strange, the algorithm should be nearly the same now (modulo RT). Still
> > I wonder that's something else on the short lived gcc processes side.
> 
> Could be.  Removing -pipe affected it quite a bit.


you could try decreasing PARENT_PENALTY to 50. I would like to see if
the scheduler *still* thinks they're interactive stuff then.

Andrea
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