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Subject: Re: [RFC patch 1/2] sched: dynamically adapt granularity with
 nr_running
From: Peter Zijlstra <peterz@infradead.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Mike Galbraith <efault@gmx.de>,
        Linus Torvalds <torvalds@linux-foundation.org>,
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Date: Mon, 13 Sep 2010 15:54:39 +0200
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On Mon, 2010-09-13 at 09:52 -0400, Steven Rostedt wrote:
> On Mon, 2010-09-13 at 10:41 +0200, Peter Zijlstra wrote:
> 
> > Yeah, without it you can starve the already running task on massive
> > forks.
> > 
> > Still, I'm not quite sure why people really care about fork() on time
> > sensitive paths, its a very expensive thing to do, pre-fork() and wake
> > when you need it, is what I would say.
> 
> Fork is used all over the place in Linux. Every shell script uses it to
> execute commands. Bad fork behavior shows up in just doing a build of
> the kernel.

Sure, but there's a difference between bad fork behaviour and the lowest
possible latency. But maybe I'm too paranoid from doing -rt, but the
first thing I'd do is get all resource allocations out from your fast
path.