Re: [tip:sched/core] sched: Turn off child_runs_first
From: Pavel Machek
Date: Wed Sep 09 2009 - 15:49:00 EST
Hi!
>
> > 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.
>
>
That kind of workload should be using vfork() anyway, and be even
>
faster because it can avoid the fork overhead, right?
Well.. one should not have to update userspace to keep
performance.... and vfork is extremely ugly interface.
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