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, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>