Messages in this thread | | | Date | Thu, 29 Nov 2012 21:57:49 -0800 | From | Andrew Morton <> | Subject | Re: [BUG REPORT] [mm-hotplug, aio] aio ring_pages can't be offlined |
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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?
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