linux-kernel - Re: [PATCH 4/5] sched: Guarantee new group-entities always have weight

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Message-ID: <20131016222225.GO10651@twins.programming.kicks-ass.net>
Date:	Thu, 17 Oct 2013 00:22:25 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Paul Turner <pjt@...gle.com>
Cc:	Ben Segall <bsegall@...gle.com>, Ingo Molnar <mingo@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/5] sched: Guarantee new group-entities always have
 weight

On Wed, Oct 16, 2013 at 03:16:44PM -0700, Paul Turner wrote:
> > Hurm.. this gives new groups a massive weight; nr_cpus * NICE_0. ISTR
> > there being some issues with this; or was that on the wakeup path where
> > a task woke on a cpu who's group entity had '0' load because it used to
> > run on another cpu -- I can't remember.
> 
> This could also arbitrarily be MIN_WEIGHT.
> 
> I don't think it actually matters, in practice the set of conditions
> for this weight to ever see use are very specific (e.g. the race
> described above). Otherwise it's always going to be re-initialized (on
> first actual enqueue) to the right value.  (NICE_0_LOAD seemed to make
> sense since this is what you'd "expect" for a new, single thread,
> autogroup/group.)

Fair enough. Thanks!
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