linux-kernel - Re: 4.2.2: NR_CPUS effectively being 1 bug

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Message-ID: <20151003065320.GE3816@twins.programming.kicks-ass.net>
Date:	Sat, 3 Oct 2015 08:53:20 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Alexey Dobriyan <adobriyan@...il.com>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: 4.2.2: NR_CPUS effectively being 1 bug

On Fri, Oct 02, 2015 at 02:00:33PM -0700, Andrew Morton wrote:
> On Fri, 2 Oct 2015 23:46:59 +0300 Alexey Dobriyan <adobriyan@...il.com> wrote:
> 
> > FYI, I've upgraded from 4.1.7 to 4.2.1 (and retested with 4.2.2) and
> > everything is scheduled on 1 CPU out of 4 (i5 760).
> > 
> > 	$ sudo cat /proc/1/status | grep cpu -i
> > 	Cpus_allowed:   1
> > 	Cpus_allowed_list:      0
> > 
> > Every process inherits this tiny cpumask.
> 
> Sell the other CPUs on ebay?
> 
> I haven't seen such a report before - maybe it rings a bell with Peter
> & Ingo?

I think this is related to some NO_HZ_FULL quackery. People seem to have
enabled stuff they've really no sane reason for.
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