From: Tejun Heo <tj@kernel.org>
To: Daniel Walker <dwalker@codeaurora.org>
Cc: mingo@elte.hu, awalls@radix.net, linux-kernel@vger.kernel.org,
jeff@garzik.org, akpm@linux-foundation.org,
rusty@rustcorp.com.au, cl@linux-foundation.org,
dhowells@redhat.com, arjan@linux.intel.com,
johannes@sipsolutions.net, oleg@redhat.com, axboe@kernel.dk
Subject: Re: Overview of concurrency managed workqueue
Date: Wed, 16 Jun 2010 16:15:05 +0200 [thread overview]
Message-ID: <4C18DC69.10704@kernel.org> (raw)
In-Reply-To: <1276697146.9309.27.camel@m0nster>
Hello,
On 06/16/2010 04:05 PM, Daniel Walker wrote:
> On Wed, 2010-06-16 at 15:45 +0200, Tejun Heo wrote:
>> On 06/16/2010 03:41 PM, Daniel Walker wrote:
>>> Any workqueue that has a thread which can be prioritized from userspace.
>>> As long as there is a thread it can usually be given a priority from
>>> userspace, so any _current_ workqueue which uses a single thread or
>>> multiple threads is an example of what I'm talking about.
>>
>> Eh... what's the use case for that? That's just so wrong. What do
>> you do after a suspend/resume cycle? Reprioritize all of them from
>> suspend/resume hooks?
>
> The use case is any situation when the user wants to give higher
> priority to some set of work items, and there's nothing wrong with that.
Come on. The user can't even know what's going on each workqueue
thread. Something you can do doesn't make it a good idea. In this
case, it's a very bad idea.
> In fact there has been a lot of work in the RT kernel related to
> workqueue prioritization ..
That frankly I don't have much idea about.
> suspend/resume shouldn't touch the thread priorities unless your tearing
> down the threads and remaking them each suspend/resume cycle from inside
> the kernel.
And here's a perfect example of why it's a very bad idea. The kernel
is *ALREADY* doing that on every suspend/resume cycle, so if you are
thinking that priorities on kernel workqueue threads were being
maintained over suspend/resume cycles, you're wrong and have been
wrong for a very long time.
Mangling workqueue thread priorities from userland is a fundamentally
broken thing to do. It's not a part of AP|BI and there's no guarantee
whatsoever that something which works currently in certain way will
keep working that way one release later. If there's something which
wants priority adjustment from userland, the right thing to do is
finding out precisely why it's necesssary and implementing a published
interface to do that.
Thanks.
--
tejun
next prev parent reply other threads:[~2010-06-16 14:16 UTC|newest]
Thread overview: 129+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-14 21:37 [PATCHSET] workqueue: concurrency managed workqueue, take#5 Tejun Heo
2010-06-14 21:37 ` [PATCH 01/30] kthread: implement kthread_data() Tejun Heo
2010-06-14 21:37 ` [PATCH 02/30] acpi: use queue_work_on() instead of binding workqueue worker to cpu0 Tejun Heo
2010-06-14 21:37 ` [PATCH 03/30] workqueue: kill RT workqueue Tejun Heo
2010-06-14 21:37 ` [PATCH 04/30] workqueue: misc/cosmetic updates Tejun Heo
2010-06-14 21:37 ` [PATCH 05/30] workqueue: merge feature parameters into flags Tejun Heo
2010-06-14 21:37 ` [PATCH 06/30] workqueue: define masks for work flags and conditionalize STATIC flags Tejun Heo
2010-06-14 21:37 ` [PATCH 07/30] workqueue: separate out process_one_work() Tejun Heo
2010-06-14 21:37 ` [PATCH 08/30] workqueue: temporarily disable workqueue tracing Tejun Heo
2010-06-15 13:29 ` Frederic Weisbecker
2010-06-15 16:37 ` Tejun Heo
2010-06-14 21:37 ` [PATCH 09/30] workqueue: kill cpu_populated_map Tejun Heo
2010-06-14 21:37 ` [PATCH 10/30] workqueue: update cwq alignement Tejun Heo
2010-06-14 21:37 ` [PATCH 11/30] workqueue: reimplement workqueue flushing using color coded works Tejun Heo
2010-06-14 21:37 ` [PATCH 12/30] workqueue: introduce worker Tejun Heo
2010-06-14 21:37 ` [PATCH 13/30] workqueue: reimplement work flushing using linked works Tejun Heo
2010-06-14 21:37 ` [PATCH 14/30] workqueue: implement per-cwq active work limit Tejun Heo
2010-06-14 21:37 ` [PATCH 15/30] workqueue: reimplement workqueue freeze using max_active Tejun Heo
2010-06-14 21:37 ` [PATCH 16/30] workqueue: introduce global cwq and unify cwq locks Tejun Heo
2010-06-14 21:37 ` [PATCH 17/30] workqueue: implement worker states Tejun Heo
2010-06-14 21:37 ` [PATCH 18/30] workqueue: reimplement CPU hotplugging support using trustee Tejun Heo
2010-06-14 21:37 ` [PATCH 19/30] workqueue: make single thread workqueue shared worker pool friendly Tejun Heo
2010-06-14 21:37 ` [PATCH 20/30] workqueue: add find_worker_executing_work() and track current_cwq Tejun Heo
2010-06-14 21:37 ` [PATCH 21/30] workqueue: carry cpu number in work data once execution starts Tejun Heo
2010-06-14 21:37 ` [PATCH 22/30] workqueue: implement WQ_NON_REENTRANT Tejun Heo
2010-06-14 21:37 ` [PATCH 23/30] workqueue: use shared worklist and pool all workers per cpu Tejun Heo
2010-06-14 21:37 ` [PATCH 24/30] workqueue: implement concurrency managed dynamic worker pool Tejun Heo
2010-06-14 21:37 ` [PATCH 25/30] workqueue: increase max_active of keventd and kill current_is_keventd() Tejun Heo
2010-06-14 21:37 ` [PATCH 26/30] workqueue: add system_wq, system_long_wq and system_nrt_wq Tejun Heo
2010-06-14 21:37 ` [PATCH 27/30] workqueue: implement DEBUGFS/workqueue Tejun Heo
2010-06-15 13:54 ` Frederic Weisbecker
2010-06-15 16:42 ` Tejun Heo
2010-06-14 21:37 ` [PATCH 28/30] workqueue: implement several utility APIs Tejun Heo
2010-06-14 21:37 ` [PATCH 29/30] libata: take advantage of cmwq and remove concurrency limitations Tejun Heo
2010-06-14 21:37 ` [PATCH 30/30] async: use workqueue for worker pool Tejun Heo
2010-06-14 21:58 ` [PATCHSET] workqueue: concurrency managed workqueue, take#5 Andrew Morton
2010-06-14 22:17 ` Tejun Heo
2010-06-14 22:31 ` Daniel Walker
2010-06-14 22:33 ` Tejun Heo
2010-06-14 22:35 ` Daniel Walker
2010-06-14 22:44 ` Tejun Heo
2010-06-14 22:49 ` Daniel Walker
2010-06-14 22:52 ` Tejun Heo
2010-06-14 22:35 ` Andrew Morton
2010-06-14 22:43 ` Tejun Heo
2010-06-14 23:06 ` Andrew Morton
2010-06-15 12:53 ` tytso
2010-06-15 16:15 ` [PATCH] SubmittingPatches: add more about patch descriptions Randy Dunlap
2010-06-15 16:33 ` Christoph Lameter
2010-06-15 18:15 ` [PATCHSET] workqueue: concurrency managed workqueue, take#5 Stefan Richter
2010-06-15 19:39 ` Tejun Heo
2010-06-15 1:20 ` Jeff Garzik
2010-06-15 18:25 ` Overview of concurrency managed workqueue Tejun Heo
2010-06-15 18:40 ` Christoph Lameter
2010-06-15 18:44 ` Tejun Heo
2010-06-15 19:43 ` Daniel Walker
2010-06-16 12:10 ` Tejun Heo
2010-06-16 13:27 ` Daniel Walker
2010-06-16 13:30 ` Tejun Heo
2010-06-16 13:41 ` Daniel Walker
2010-06-16 13:45 ` Tejun Heo
2010-06-16 14:05 ` Daniel Walker
2010-06-16 14:15 ` Tejun Heo [this message]
2010-06-16 14:34 ` Daniel Walker
2010-06-16 14:50 ` Tejun Heo
2010-06-16 15:11 ` Daniel Walker
2010-06-16 15:50 ` Tejun Heo
2010-06-16 16:30 ` Daniel Walker
2010-06-16 16:55 ` Tejun Heo
2010-06-16 18:22 ` Daniel Walker
2010-06-16 18:46 ` Tejun Heo
2010-06-16 19:20 ` Tejun Heo
2010-06-16 19:46 ` Daniel Walker
2010-06-16 19:58 ` Tejun Heo
2010-06-17 5:29 ` Florian Mickler
2010-06-17 6:21 ` Florian Mickler
2010-06-17 8:28 ` Tejun Heo
2010-06-17 18:03 ` Daniel Walker
2010-06-18 6:36 ` Florian Mickler
2010-06-18 16:38 ` Daniel Walker
2010-06-16 19:36 ` Daniel Walker
2010-06-16 19:52 ` Tejun Heo
2010-06-16 20:19 ` Daniel Walker
2010-06-16 20:24 ` Tejun Heo
2010-06-16 20:40 ` Daniel Walker
2010-06-16 21:41 ` Tejun Heo
2010-06-17 23:15 ` Andrew Morton
2010-06-18 8:03 ` Tejun Heo
2010-06-18 8:22 ` Tejun Heo
2010-06-18 17:29 ` Daniel Walker
2010-06-16 18:31 ` Stefan Richter
2010-06-16 18:41 ` Daniel Walker
2010-06-17 12:01 ` Andy Walls
2010-06-17 16:56 ` Daniel Walker
2010-06-17 23:16 ` Andrew Morton
2010-06-18 7:16 ` Tejun Heo
2010-06-18 7:31 ` Andrew Morton
2010-06-18 8:09 ` Tejun Heo
2010-06-18 17:02 ` Andrew Morton
2010-06-18 17:28 ` Tejun Heo
2010-06-19 15:53 ` [PATCH] kthread: implement kthread_worker Tejun Heo
2010-06-21 20:33 ` Randy Dunlap
2010-06-22 7:31 ` Tejun Heo
2010-06-19 8:38 ` Overview of concurrency managed workqueue Andi Kleen
2010-06-19 8:40 ` Tejun Heo
2010-06-19 8:55 ` Andi Kleen
2010-06-19 9:01 ` Tejun Heo
2010-06-19 9:08 ` Andi Kleen
2010-06-19 9:12 ` Tejun Heo
2010-06-19 9:15 ` Andi Kleen
2010-06-19 9:17 ` Tejun Heo
2010-06-19 9:27 ` Andi Kleen
2010-06-19 9:42 ` Tejun Heo
2010-06-19 12:20 ` Andi Kleen
2010-06-19 12:48 ` Tejun Heo
2010-06-17 22:28 ` Daniel Walker
2010-06-16 6:55 ` Florian Mickler
2010-06-16 12:22 ` Tejun Heo
2010-06-16 13:37 ` Johannes Berg
2010-06-16 13:39 ` Tejun Heo
2010-06-16 13:42 ` Johannes Berg
2010-06-17 23:14 ` Andrew Morton
2010-06-17 23:25 ` Joel Becker
2010-06-17 23:56 ` Andrew Morton
2010-06-18 7:15 ` Tejun Heo
2010-06-18 7:31 ` Tejun Heo
2010-06-15 18:29 ` [PATCHSET] workqueue: concurrency managed workqueue, take#5 Stefan Richter
2010-06-15 18:40 ` Tejun Heo
2010-06-15 20:29 ` Stefan Richter
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