On Fri, 30 Nov 2012 11:42:05 +0800 Lin Feng <linfeng@xxxxxxxxxxxxxx> wrote:
hi Andrew,
On 11/30/2012 07:39 AM, Andrew Morton wrote:Tricky.the offline retry timeout duration is 2 minutes, so to O_DIRECT pages
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).
seem maybe not a problem for the moment.
thanks for your advice.
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.
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?