From: Minchan Kim <minchan@kernel.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Subject: Re: needed lru_add_drain_all() change
Date: Wed, 27 Jun 2012 09:55:10 +0900 [thread overview]
Message-ID: <4FEA59EE.8060804@kernel.org> (raw)
In-Reply-To: <20120626143703.396d6d66.akpm@linux-foundation.org>
On 06/27/2012 06:37 AM, Andrew Morton wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=43811
>
> lru_add_drain_all() uses schedule_on_each_cpu(). But
> schedule_on_each_cpu() hangs if a realtime thread is spinning, pinned
> to a CPU. There's no intention to change the scheduler behaviour, so I
> think we should remove schedule_on_each_cpu() from the kernel.
>
> The biggest user of schedule_on_each_cpu() is lru_add_drain_all().
>
> Does anyone have any thoughts on how we can do this? The obvious
> approach is to declare these:
>
> static DEFINE_PER_CPU(struct pagevec[NR_LRU_LISTS], lru_add_pvecs);
> static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs);
> static DEFINE_PER_CPU(struct pagevec, lru_deactivate_pvecs);
One more
static DEFINE_PER_CPU(struct pagevec, activate_page_pvecs);
>
> to be irq-safe and use on_each_cpu(). lru_rotate_pvecs is already
> irq-safe and converting lru_add_pvecs and lru_deactivate_pvecs looks
> pretty simple.
Yes. Changing looks simple.
I'm okay with lru_[activate_page|deactivate]_pvecs because it's not hot
but lru_rotate_pvecs is hotter than others. 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?
--
Kind regards,
Minchan Kim
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next prev parent reply other threads:[~2012-06-27 0:55 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 [this message]
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
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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