From: Peter Zijlstra <peterz@infradead.org>
To: "Nikunj A. Dadhania" <nikunj@linux.vnet.ibm.com>
Cc: mingo@elte.hu, linux-kernel@vger.kernel.org,
vatsa@linux.vnet.ibm.com, bharata@linux.vnet.ibm.com,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
paulus <paulus@samba.org>
Subject: Re: [RFC PATCH 0/4] Gang scheduling in CFS
Date: Mon, 19 Dec 2011 16:51:41 +0100 [thread overview]
Message-ID: <1324309901.24621.14.camel@twins> (raw)
In-Reply-To: <20111219083141.32311.9429.stgit@abhimanyu.in.ibm.com>
On Mon, 2011-12-19 at 14:03 +0530, Nikunj A. Dadhania wrote:
> The following patches implements gang scheduling. These patches
> are *highly* experimental in nature and are not proposed for
> inclusion at this time.
Nor will they ever be, I've always strongly opposed the whole concept
and I'm not about to change my mind. Gang scheduling is a scalability
nightmare.
> Gang scheduling can be helpful in virtualization scenario. It will
> help in avoiding the lock-holder-preemption[1] problem and other
> benefits include improved lock-acquisition times. This feature
> will help address some limitations of KVM on Power
Use paravirt ticket locks or a pause-loop-filter like thing.
> On Power, we have an interesting hardware restriction on guests
> running across SMT theads: on any single core, we can only run one
> mm context at any given time.
OMFG are your hardware engineers insane?
Anyway, I had a look at your patches and I don't see how could ever
work. You gang-schedule cgroup entities, but there's no guarantee the
load-balancer will have at least one task for each group on every cpu.
next prev parent reply other threads:[~2011-12-19 15:52 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-19 8:33 [RFC PATCH 0/4] Gang scheduling in CFS Nikunj A. Dadhania
2011-12-19 8:34 ` [RFC PATCH 1/4] sched: Adding cpu.gang file to cpu cgroup Nikunj A. Dadhania
2011-12-19 8:34 ` [RFC PATCH 2/4] sched: Adding gang scheduling infrastrucure Nikunj A. Dadhania
2011-12-19 15:51 ` Peter Zijlstra
2011-12-19 16:51 ` Peter Zijlstra
2011-12-20 1:43 ` Nikunj A Dadhania
2011-12-20 1:39 ` Nikunj A Dadhania
2011-12-19 8:34 ` [RFC PATCH 3/4] sched: Gang using set_next_buddy Nikunj A. Dadhania
2011-12-19 8:35 ` [RFC PATCH 4/4] sched:Implement set_gang_buddy Nikunj A. Dadhania
2011-12-19 15:51 ` Peter Zijlstra
2011-12-20 1:43 ` Nikunj A Dadhania
2011-12-26 2:30 ` Nikunj A Dadhania
2011-12-19 11:23 ` [RFC PATCH 0/4] Gang scheduling in CFS Ingo Molnar
2011-12-19 11:44 ` Avi Kivity
2011-12-19 11:50 ` Nikunj A Dadhania
2011-12-19 11:59 ` Avi Kivity
2011-12-19 12:06 ` Nikunj A Dadhania
2011-12-19 12:50 ` Avi Kivity
2011-12-19 13:09 ` Nikunj A Dadhania
2011-12-19 11:45 ` Nikunj A Dadhania
2011-12-19 13:22 ` Nikunj A Dadhania
2011-12-19 16:28 ` Ingo Molnar
2011-12-21 10:39 ` Nikunj A Dadhania
2011-12-21 10:43 ` Avi Kivity
2011-12-23 3:20 ` Nikunj A Dadhania
2011-12-23 10:36 ` Ingo Molnar
2011-12-25 10:58 ` Avi Kivity
2011-12-25 15:45 ` Avi Kivity
2011-12-26 3:14 ` Nikunj A Dadhania
2011-12-26 9:05 ` Avi Kivity
2011-12-26 11:33 ` Nikunj A Dadhania
2011-12-26 11:41 ` Avi Kivity
2011-12-27 1:47 ` Nikunj A Dadhania
2011-12-27 9:15 ` Avi Kivity
2011-12-27 10:24 ` Nikunj A Dadhania
2011-12-27 3:15 ` Nikunj A Dadhania
2011-12-27 9:17 ` Avi Kivity
2011-12-27 9:44 ` Nikunj A Dadhania
2011-12-27 9:51 ` Avi Kivity
2011-12-27 10:10 ` Nikunj A Dadhania
2011-12-27 10:34 ` Avi Kivity
2011-12-27 10:43 ` Nikunj A Dadhania
2011-12-27 10:53 ` Avi Kivity
2011-12-30 9:51 ` Ingo Molnar
2011-12-30 10:10 ` Nikunj A Dadhania
2011-12-31 2:21 ` Nikunj A Dadhania
2012-01-02 4:20 ` Nikunj A Dadhania
2012-01-02 9:39 ` Avi Kivity
2012-01-02 10:22 ` Nikunj A Dadhania
2012-01-02 9:37 ` Avi Kivity
2012-01-02 10:30 ` Nikunj A Dadhania
2012-01-02 13:33 ` Avi Kivity
2012-01-04 10:52 ` Nikunj A Dadhania
2012-01-04 14:41 ` Avi Kivity
2012-01-04 14:56 ` Srivatsa Vaddagiri
2012-01-04 17:13 ` Avi Kivity
2012-01-05 6:57 ` Nikunj A Dadhania
2012-01-04 16:47 ` Rik van Riel
2012-01-04 17:16 ` Avi Kivity
2012-01-04 20:56 ` Rik van Riel
2012-01-04 21:31 ` Peter Zijlstra
2012-01-04 21:41 ` Avi Kivity
2012-01-05 9:10 ` Ingo Molnar
2012-02-20 8:08 ` Nikunj A Dadhania
2012-02-20 8:14 ` Ingo Molnar
2012-02-20 10:51 ` Peter Zijlstra
2012-02-20 11:53 ` Nikunj A Dadhania
2012-02-20 12:02 ` Srivatsa Vaddagiri
2012-02-20 12:14 ` Peter Zijlstra
2012-01-05 2:10 ` Nikunj A Dadhania
2011-12-19 15:51 ` Peter Zijlstra [this message]
2011-12-19 16:09 ` Alan Cox
2011-12-19 22:10 ` Benjamin Herrenschmidt
2011-12-20 1:56 ` Nikunj A Dadhania
2011-12-20 8:52 ` Jeremy Fitzhardinge
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