From: Tejun Heo <tj@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: torvalds@linux-foundation.org, awalls@radix.net,
linux-kernel@vger.kernel.org, jeff@garzik.org, mingo@elte.hu,
akpm@linux-foundation.org, jens.axboe@oracle.com,
rusty@rustcorp.com.au, cl@linux-foundation.org,
dhowells@redhat.com, arjan@linux.intel.com, avi@redhat.com,
johannes@sipsolutions.net, andi@firstfloor.org
Subject: Re: workqueue thing
Date: Wed, 23 Dec 2009 12:48:51 +0900 [thread overview]
Message-ID: <4B319323.5030704@kernel.org> (raw)
In-Reply-To: <1261479857.4937.18.camel@laptop>
Hello,
On 12/22/2009 08:04 PM, Peter Zijlstra wrote:
> On Tue, 2009-12-22 at 08:50 +0900, Tejun Heo wrote:
>>> Also, I think that whole move tasks back on online stuff is utter crazy,
>>> just move then to another cpu and leave them there.
>>
>> Can you be more specific? Why is it crazy when moving to online but
>> !active cpu is necessary anyway?
>
> because its extra (and above all ugly code) that serves no purpose what
> so ever.
The forward progress guarantee requires rescuers to migrate to online
but !active CPUs during CPU_DOWN_PREPARE, so the only extra code
necessary for migrating back remaining workers when a CPU comes back
online is the code to actually do that. That's only a couple tens of
lines of code in the trustee thread.
Now, the other option would to leave those unbound workers alone and
make sure they don't take up new works once new CPUs come online which
would require code in hotter path and results in less consistent
behavior. The tradeoff seems pretty obvious to me. Doesn't it?
Thanks.
--
tejun
next prev parent reply other threads:[~2009-12-23 3:46 UTC|newest]
Thread overview: 104+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-12-18 12:57 Tejun Heo
2009-12-18 12:57 ` [PATCH 01/27] sched: rename preempt_notifiers to sched_notifiers and refactor implementation Tejun Heo
2009-12-18 12:57 ` [PATCH 02/27] sched: refactor try_to_wake_up() Tejun Heo
2009-12-18 12:57 ` [PATCH 03/27] sched: implement __set_cpus_allowed() Tejun Heo
2009-12-18 12:57 ` [PATCH 04/27] sched: make sched_notifiers unconditional Tejun Heo
2009-12-18 12:57 ` [PATCH 05/27] sched: add wakeup/sleep sched_notifiers and allow NULL notifier ops Tejun Heo
2009-12-18 12:57 ` [PATCH 06/27] sched: implement try_to_wake_up_local() Tejun Heo
2009-12-18 12:57 ` [PATCH 07/27] acpi: use queue_work_on() instead of binding workqueue worker to cpu0 Tejun Heo
2009-12-18 12:57 ` [PATCH 08/27] stop_machine: reimplement without using workqueue Tejun Heo
2009-12-18 12:57 ` [PATCH 09/27] workqueue: misc/cosmetic updates Tejun Heo
2009-12-18 12:57 ` [PATCH 10/27] workqueue: merge feature parameters into flags Tejun Heo
2009-12-18 12:57 ` [PATCH 11/27] workqueue: define both bit position and mask for work flags Tejun Heo
2009-12-18 12:57 ` [PATCH 12/27] workqueue: separate out process_one_work() Tejun Heo
2009-12-18 12:57 ` [PATCH 13/27] workqueue: temporarily disable workqueue tracing Tejun Heo
2009-12-18 12:57 ` [PATCH 14/27] workqueue: kill cpu_populated_map Tejun Heo
2009-12-18 12:57 ` [PATCH 15/27] workqueue: update cwq alignement Tejun Heo
2009-12-18 12:57 ` [PATCH 16/27] workqueue: reimplement workqueue flushing using color coded works Tejun Heo
2009-12-18 12:57 ` [PATCH 17/27] workqueue: introduce worker Tejun Heo
2009-12-18 12:57 ` [PATCH 18/27] workqueue: reimplement work flushing using linked works Tejun Heo
2009-12-18 12:58 ` [PATCH 19/27] workqueue: implement per-cwq active work limit Tejun Heo
2009-12-18 12:58 ` [PATCH 20/27] workqueue: reimplement workqueue freeze using max_active Tejun Heo
2009-12-18 12:58 ` [PATCH 21/27] workqueue: introduce global cwq and unify cwq locks Tejun Heo
2009-12-18 12:58 ` [PATCH 22/27] workqueue: implement worker states Tejun Heo
2009-12-18 12:58 ` [PATCH 23/27] workqueue: reimplement CPU hotplugging support using trustee Tejun Heo
2009-12-18 12:58 ` [PATCH 24/27] workqueue: make single thread workqueue shared worker pool friendly Tejun Heo
2009-12-18 12:58 ` [PATCH 25/27] workqueue: use shared worklist and pool all workers per cpu Tejun Heo
2009-12-18 12:58 ` [PATCH 26/27] workqueue: implement concurrency managed dynamic worker pool Tejun Heo
2009-12-18 12:58 ` [PATCH 27/27] workqueue: increase max_active of keventd and kill current_is_keventd() Tejun Heo
2009-12-18 13:00 ` SUBJ: [RFC PATCHSET] concurrency managed workqueue, take#2 Tejun Heo
2009-12-18 13:03 ` Tejun Heo
2009-12-18 13:45 ` workqueue thing Peter Zijlstra
2009-12-18 13:50 ` Andi Kleen
2009-12-18 15:01 ` Arjan van de Ven
2009-12-21 3:19 ` Tejun Heo
2009-12-21 9:17 ` Jens Axboe
2009-12-21 10:35 ` Peter Zijlstra
2009-12-21 11:09 ` Andi Kleen
2009-12-21 11:17 ` Arjan van de Ven
2009-12-21 11:33 ` Andi Kleen
2009-12-21 13:18 ` Tejun Heo
2009-12-21 11:11 ` Arjan van de Ven
2009-12-21 13:22 ` Tejun Heo
2009-12-21 13:53 ` Arjan van de Ven
2009-12-21 14:19 ` Tejun Heo
2009-12-21 15:19 ` Arjan van de Ven
2009-12-22 0:00 ` Tejun Heo
2009-12-22 11:10 ` Peter Zijlstra
2009-12-22 17:20 ` Linus Torvalds
2009-12-22 17:47 ` Peter Zijlstra
2009-12-22 18:07 ` Andi Kleen
2009-12-22 18:20 ` Peter Zijlstra
2009-12-23 8:17 ` Stijn Devriendt
2009-12-23 8:43 ` Peter Zijlstra
2009-12-23 9:01 ` Stijn Devriendt
2009-12-22 18:28 ` Linus Torvalds
2009-12-23 8:06 ` Johannes Berg
2009-12-23 3:37 ` Tejun Heo
2009-12-23 6:52 ` Herbert Xu
2009-12-23 8:00 ` Steffen Klassert
2009-12-23 8:01 ` [PATCH 0/2] Parallel crypto/IPsec v7 Steffen Klassert
2009-12-23 8:03 ` [PATCH 1/2] padata: generic parallelization/serialization interface Steffen Klassert
2009-12-23 8:04 ` [PATCH 2/2] crypto: pcrypt - Add pcrypt crypto parallelization wrapper Steffen Klassert
2010-01-07 5:39 ` [PATCH 0/2] Parallel crypto/IPsec v7 Herbert Xu
2010-01-16 9:44 ` David Miller
2009-12-18 15:30 ` workqueue thing Linus Torvalds
2009-12-18 15:39 ` Ingo Molnar
2009-12-18 15:39 ` Peter Zijlstra
2009-12-18 15:47 ` Linus Torvalds
2009-12-18 15:53 ` Peter Zijlstra
2009-12-21 3:04 ` Tejun Heo
2009-12-21 9:22 ` Peter Zijlstra
2009-12-21 13:30 ` Tejun Heo
2009-12-21 14:26 ` Peter Zijlstra
2009-12-21 23:50 ` Tejun Heo
2009-12-22 11:00 ` Peter Zijlstra
2009-12-22 11:03 ` Peter Zijlstra
2009-12-23 3:43 ` Tejun Heo
2009-12-22 11:04 ` Peter Zijlstra
2009-12-23 3:48 ` Tejun Heo [this message]
2009-12-22 11:06 ` Peter Zijlstra
2009-12-23 4:18 ` Tejun Heo
2009-12-23 4:42 ` Linus Torvalds
2009-12-23 6:02 ` Ingo Molnar
2009-12-23 6:13 ` Jeff Garzik
2009-12-23 7:53 ` Ingo Molnar
2009-12-23 8:41 ` Peter Zijlstra
2009-12-23 10:25 ` Jeff Garzik
2009-12-23 13:33 ` Stefan Richter
2009-12-23 14:20 ` Mark Brown
2009-12-23 7:09 ` Tejun Heo
2009-12-23 8:01 ` Ingo Molnar
2009-12-23 8:12 ` Ingo Molnar
2009-12-23 8:32 ` Tejun Heo
2009-12-23 8:42 ` Ingo Molnar
2009-12-23 8:27 ` Tejun Heo
2009-12-23 8:37 ` Ingo Molnar
2009-12-23 8:49 ` Tejun Heo
2009-12-23 8:49 ` Ingo Molnar
2009-12-23 9:03 ` Tejun Heo
2009-12-23 13:40 ` Stefan Richter
2009-12-23 13:43 ` Stefan Richter
2009-12-23 8:25 ` Arjan van de Ven
2009-12-23 13:00 ` Stefan Richter
2009-12-23 8:31 ` Stijn Devriendt
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