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Date: Fri, 30 Nov 2012 11:42:05 +0800 From: Lin Feng <linfeng@...fujitsu.com> To: Andrew Morton <akpm@...ux-foundation.org> CC: viro@...iv.linux.org.uk, bcrl@...ck.org, kamezawa.hiroyu@...fujitsu.com, mhocko@...e.cz, hughd@...gle.com, cl@...ux.com, mgorman@...e.de, minchan@...nel.org, isimatu.yasuaki@...fujitsu.com, laijs@...fujitsu.com, wency@...fujitsu.com, tangchen@...fujitsu.com, linux-fsdevel@...r.kernel.org, linux-aio@...ck.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org Subject: Re: [BUG REPORT] [mm-hotplug, aio] aio ring_pages can't be offlined 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. Thanks, linfeng -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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