|| ||Andrew Morton <akpm-AT-linux-foundation.org> |
|| ||Tejun Heo <tj-AT-kernel.org> |
|| ||Re: Overview of concurrency managed workqueue |
|| ||Thu, 17 Jun 2010 16:15:39 -0700|
|| ||Daniel Walker <dwalker-AT-codeaurora.org>, mingo-AT-elte.hu,
awalls-AT-radix.net, linux-kernel-AT-vger.kernel.org, jeff-AT-garzik.org,
johannes-AT-sipsolutions.net, oleg-AT-redhat.com, axboe-AT-kernel.dk|
|| ||Article, Thread
On Wed, 16 Jun 2010 18:55:05 +0200
Tejun Heo <firstname.lastname@example.org> wrote:
> It was about using wq for cpu intensive / RT stuff. Linus said,
> So stop arguing about irrelevancies. Nobody uses workqueues for RT
> or for CPU-intensive crap. It's not what they were designed for, or
> used for.
kernel/padata.c uses workqueues for cpu-intensive work, as I understand
I share Daniel's concerns here. Being able to set a worker thread's
priority or policy isn't a crazy thing. Also one might want to specify
that a work item be executed on one of a node's CPUs, or within a
cpuset's CPUs, maybe other stuff. I have vague feelings that there's
already code in the kernel somewhere which does some of these things.
(Please remind me what your patches did about create_rt_workqueue and
(Please note that drivers/media/video/ivtv/ivtv-irq.c is currently
running sched_setscheduler() against a workqueue thread of its own
creation, so we have precedent).
If someone wants realtime service for a work item then at present, the
way to do that is to create your own kernel threads, set their policy
and start feeding them work items. That sounds like a sensible
requirement and implementation to me. But how does it translate into
the new implementation?
The priority/policy logically attaches to the work itself, not to the
thread which serves it. So one would want to be able to provide that
info at queue_work()-time. Could the workqueue core then find a thread,
set its policy/priority, schedule it and then let the CPU scheduler do
its usual thing with it?
That doesn't sound too bad? Add policy/priority/etc fields to the
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