From: Minchan Kim <minchan@kernel.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, KOSAKI Motohiro <kosaki.motohiro@gmail.com>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: needed lru_add_drain_all() change
Date: Wed, 27 Jun 2012 15:33:09 +0900 [thread overview]
Message-ID: <4FEAA925.9020202@kernel.org> (raw)
In-Reply-To: <20120626225544.068df1b9.akpm@linux-foundation.org>
On 06/27/2012 02:55 PM, Andrew Morton wrote:
> On Wed, 27 Jun 2012 14:41:39 +0900 Minchan Kim <minchan@kernel.org> wrote:
>
>> On 06/27/2012 02:12 PM, Andrew Morton wrote:
>>
>>> On Wed, 27 Jun 2012 11:09:31 +0900 Minchan Kim <minchan@kernel.org> wrote:
>>>
>>>> On 06/27/2012 10:15 AM, Andrew Morton wrote:
>>>>
>>>>>> Considering mlock and CPU pinning
>>>>>>> of realtime thread is very rare, it might be rather expensive solution.
>>>>>>> Unfortunately, I have no idea better than you suggested. :(
>>>>>>>
>>>>>>> And looking 8891d6da17, mlock's lru_add_drain_all isn't must.
>>>>>>> If it's really bother us, couldn't we remove it?
>>>>> "grep lru_add_drain_all mm/*.c". They're all problematic.
>>>>
>>>>
>>>> Yeb but I'm not sure such system modeling is good.
>>>> Potentially, It could make problem once we use workqueue of other CPU.
>>>
>>> whut?
>>>
>>> My suggestion is that we switch lru_add_drain_all() to on_each_cpu()
>>> and delete schedule_on_each_cpu(). No workqueues.
>>
>>
>> Current problem is that RT thread doesn't yield his CPU so other tasks can't be scheduled in.
>> schedule_on_each_cpu uses system workqueue so if there are any user to try using
>> workqueue for the CPU(ex, schedule_work_on), he can make trouble, too.
>> So my question is I doubt such greedy RT thread modeling is good.
>>
>
> There's no way of fixing this without significantly degrading the
> service which rt priority offers. As we don't wish to degrade that
> service, schedule_work_on() and schedule_on_each_cpu() cannot be
> implemented reliably. So we delete them.
Okay. I'm not against strongly if local_irq_save/restore isn't expensive
as a first step for removing them because I have no good idea.
I want to add some comment on schedule_work_on and friends.
"You shouldn't use it any more and we will try to remove this".
Anyway, let's wait further answer, especially, RT folks.
--
Kind regards,
Minchan Kim
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next prev parent reply other threads:[~2012-06-27 6:33 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-26 21:37 needed lru_add_drain_all() change Andrew Morton
2012-06-27 0:55 ` Minchan Kim
2012-06-27 1:15 ` Andrew Morton
2012-06-27 1:20 ` Minchan Kim
2012-06-27 1:29 ` Andrew Morton
2012-06-27 2:09 ` Minchan Kim
2012-06-27 5:12 ` Andrew Morton
2012-06-27 5:41 ` Minchan Kim
2012-06-27 5:55 ` Andrew Morton
2012-06-27 6:33 ` Minchan Kim [this message]
2012-06-27 6:41 ` Andrew Morton
2012-06-27 10:27 ` Peter Zijlstra
2012-06-27 6:46 ` Andrew Morton
2012-06-27 10:31 ` Peter Zijlstra
2012-06-27 12:04 ` Peter Zijlstra
2012-06-28 6:23 ` KOSAKI Motohiro
2012-06-29 3:47 ` Kamezawa Hiroyuki
2012-06-28 7:43 ` Kamezawa Hiroyuki
2012-06-28 23:42 ` Minchan Kim
2012-06-29 3:24 ` Kamezawa Hiroyuki
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