From: Jeff Moyer <jmoyer@redhat.com>
To: Jens Axboe <jaxboe@fusionio.com>
Cc: "linux-kernel\@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm\@kvack.org" <linux-mm@kvack.org>,
Zach Brown <zab@redhat.com>,
tj@kernel.org, Peter Zijlstra <pzijlstr@redhat.com>,
Ingo <mingo@redhat.com>
Subject: Re: [patch,v2] bdi: add a user-tunable cpu_list for the bdi flusher threads
Date: Tue, 04 Dec 2012 17:26:26 -0500 [thread overview]
Message-ID: <x494nk1pi7h.fsf@segfault.boston.devel.redhat.com> (raw)
In-Reply-To: <50BE5C99.6070703@fusionio.com> (Jens Axboe's message of "Tue, 4 Dec 2012 21:27:05 +0100")
Jens Axboe <jaxboe@fusionio.com> writes:
>>>> @@ -437,6 +488,14 @@ static int bdi_forker_thread(void *ptr)
>>>> spin_lock_bh(&bdi->wb_lock);
>>>> bdi->wb.task = task;
>>>> spin_unlock_bh(&bdi->wb_lock);
>>>> + mutex_lock(&bdi->flusher_cpumask_mutex);
>>>> + ret = set_cpus_allowed_ptr(task,
>>>> + bdi->flusher_cpumask);
>>>> + mutex_unlock(&bdi->flusher_cpumask_mutex);
>>>
>>> It'd be very useful if we had a kthread_create_cpu_on_cpumask() instead
>>> of a _node() variant, since the latter could easily be implemented on
>>> top of the former. But not really a show stopper for the patch...
>>
>> Hmm, if it isn't too scary, I might give this a try.
>
> Should not be, pretty much just removing the node part of the create
> struct passed in and making it a cpumask. And for the on_node() case,
> cpumask_of_ndoe() will do the trick.
I think it's a bit more involved than that. If you look at
kthread_create_on_node, the node portion only applies to where the
memory comes from, it says nothing of scheduling. To whit:
/*
* root may have changed our (kthreadd's) priority or CPU mask.
* The kernel thread should not inherit these properties.
*/
sched_setscheduler_nocheck(create.result, SCHED_NORMAL, ¶m);
set_cpus_allowed_ptr(create.result, cpu_all_mask);
So, if I were to make the change you suggested, I would be modifying the
existing behaviour. The way things stand, I think
kthread_create_on_node violates the principal of least surprise. ;-) I
would prefer a variant that affected scheduling behaviour as well as
memory placement. Tejun, Peter, Ingo, what are your opinions?
Cheers,
Jeff
next prev parent reply other threads:[~2012-12-04 22:26 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-03 18:53 [patch,v2] bdi: add a user-tunable cpu_list for the bdi flusher threads Jeff Moyer
2012-12-04 2:34 ` Dave Chinner
2012-12-04 14:42 ` Jeff Moyer
2012-12-04 20:35 ` Dave Chinner
2012-12-04 20:14 ` Jens Axboe
2012-12-04 20:23 ` Jeff Moyer
2012-12-04 20:27 ` Jens Axboe
2012-12-04 22:26 ` Jeff Moyer [this message]
2012-12-05 7:43 ` Jens Axboe
2012-12-06 18:01 ` Tejun Heo
2012-12-06 18:08 ` Jeff Moyer
2012-12-06 18:13 ` Tejun Heo
2012-12-06 18:19 ` Jens Axboe
2012-12-06 18:22 ` Tejun Heo
2012-12-06 18:33 ` Jeff Moyer
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