From: Andrew Morton <akpm@linux-foundation.org>
To: Lin Feng <linfeng@cn.fujitsu.com>
Cc: viro@zeniv.linux.org.uk, bcrl@kvack.org,
kamezawa.hiroyu@jp.fujitsu.com, mhocko@suse.cz, hughd@google.com,
cl@linux.com, mgorman@suse.de, minchan@kernel.org,
isimatu.yasuaki@jp.fujitsu.com, laijs@cn.fujitsu.com,
wency@cn.fujitsu.com, tangchen@cn.fujitsu.com,
linux-fsdevel@vger.kernel.org, linux-aio@kvack.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [BUG REPORT] [mm-hotplug, aio] aio ring_pages can't be offlined
Date: Thu, 29 Nov 2012 21:57:49 -0800 [thread overview]
Message-ID: <20121129215749.acfd872a.akpm@linux-foundation.org> (raw)
In-Reply-To: <50B82B0D.8010206@cn.fujitsu.com>
On Fri, 30 Nov 2012 11:42:05 +0800 Lin Feng <linfeng@cn.fujitsu.com> wrote:
> hi Andrew,
>
> On 11/30/2012 07:39 AM, Andrew Morton wrote:
> > Tricky.
> >
> > I expect the same problem would occur with pages which are under
> > O_DIRECT I/O. Obviously O_DIRECT pages won't be pinned for such long
> > periods, but the durations could still be lengthy (seconds).
> the offline retry timeout duration is 2 minutes, so to O_DIRECT pages
> seem maybe not a problem for the moment.
> >
> > Worse is a futex page, which could easily remain pinned indefinitely.
> >
> > The best I can think of is to make changes in or around
> > get_user_pages(), to steal the pages from userspace and replace them
> > with non-movable ones before pinning them. The performance cost of
> > something like this would surely be unacceptable for direct-io, but
> > maybe OK for the aio ring and futexes.
> thanks for your advice.
> I want to limit the impact as little as possible, as mentioned above,
> direct-io seems not a problem, we needn't touch them. Maybe we can
> just change the use of get_user_pages()(in or around) such as aio
> ring pages. I will try to find a way to do this.
What about futexes?
next prev parent reply other threads:[~2012-11-30 5:57 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-29 6:54 [BUG REPORT] [mm-hotplug, aio] aio ring_pages can't be offlined Lin Feng
2012-11-29 23:39 ` Andrew Morton
2012-11-30 0:04 ` Zach Brown
2012-11-30 3:39 ` Lin Feng
2012-11-30 3:42 ` Lin Feng
2012-11-30 5:57 ` Andrew Morton [this message]
2012-11-30 7:01 ` Lin Feng
2012-11-30 7:55 ` Andrew Morton
2012-11-30 10:29 ` Lin Feng
2012-11-30 10:47 ` Andrew Morton
2012-12-03 3:00 ` Lin Feng
2012-11-30 11:00 ` Mel Gorman
2012-12-03 2:52 ` Lin Feng
2012-12-03 11:37 ` Mel Gorman
2012-11-30 7:13 ` Kamezawa Hiroyuki
2012-11-30 8:00 ` Andrew Morton
2012-11-30 10:57 ` Mel Gorman
2012-11-30 15:24 ` Domenico Andreoli
2012-12-03 2:05 ` Lin Feng
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