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From: Peter Zijlstra <peterz@infradead.org>
To: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@elte.hu>,
	ktkhai@parallels.com
Subject: Re: sched_setscheduler() vs idle_balance() race
Date: Mon, 1 Jun 2015 10:14:29 +0200	[thread overview]
Message-ID: <20150601081429.GP19282@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1432925336.8727.29.camel@gmail.com>

On Fri, May 29, 2015 at 08:48:56PM +0200, Mike Galbraith wrote:
> 
> P.S. intel_idle is not all that wonderful on this box.
> 
> -   78.31%  [kernel]       [k] _raw_spin_lock                                                                                                                                                                                              ▒
>    - _raw_spin_lock                                                                                                                                                                                                                        ▒
>       - 94.91% tick_broadcast_oneshot_control                                                                                                                                                                                              ▒

Your DL980 G7 has E7-4800 parts in, right? Which if Wikipedia is
correct, resolves to a Nehalem-EX.

Now the NHM-EX has a fun 'feature' that for (some?) idle states the
local timer stops, so we have to revert back to a global broadcast
timer.

Now go count the number of cpus on your box and then imagine a global
spinlock, oh wait, you already found it ^ :-)

  reply	other threads:[~2015-06-01  8:14 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-05-28  7:43 sched_setscheduler() vs idle_balance() race Mike Galbraith
2015-05-28 11:51 ` Peter Zijlstra
2015-05-28 12:04   ` Mike Galbraith
2015-05-28 12:06     ` Peter Zijlstra
2015-05-28 12:32       ` Mike Galbraith
2015-05-28 13:53 ` Peter Zijlstra
2015-05-28 14:54   ` Mike Galbraith
2015-05-28 15:24     ` Peter Zijlstra
2015-05-29 18:30       ` Mike Galbraith
2015-05-29 18:48         ` Mike Galbraith
2015-06-01  8:14           ` Peter Zijlstra [this message]
2015-06-01  8:16         ` Peter Zijlstra
2015-06-01 10:00           ` Mike Galbraith
2015-05-28 16:59   ` Kirill Tkhai
2015-05-30 13:08   ` Mike Galbraith
2015-05-31  6:39     ` Mike Galbraith
2015-06-01  8:24       ` Peter Zijlstra
2015-06-01  8:19     ` Peter Zijlstra

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