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Date: Wed, 9 Sep 2009 13:57:24 -0400
From: Theodore Tso <tytso@mit.edu>
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Subject: Re: [tip:sched/core] sched: Turn off child_runs_first
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On Wed, Sep 09, 2009 at 03:37:07PM +0000, tip-bot for Mike Galbraith wrote:
> Commit-ID:  2bba22c50b06abe9fd0d23933b1e64d35b419262
> Gitweb:     http://git.kernel.org/tip/2bba22c50b06abe9fd0d23933b1e64d35b419262
> Author:     Mike Galbraith <efault@gmx.de>
> AuthorDate: Wed, 9 Sep 2009 15:41:37 +0200
> Committer:  Ingo Molnar <mingo@elte.hu>
> CommitDate: Wed, 9 Sep 2009 17:30:05 +0200
> 
> sched: Turn off child_runs_first
> 
> Set child_runs_first default to off.
> 
> It hurts 'optimal' make -j<NR_CPUS> workloads as make jobs
> get preempted by child tasks, reducing parallelism.

Wasn't one of the reasons why we historically did child_runs_first was
so that for fork/exit workloads, the child has a chance to exec the
new process?  If the parent runs first, then more pages will probably
need to be COW'ed.

					- Ted