ntdll: Use lockfree implementation for get_cached_fd. (try 3)

[Bruno Jesus]

On Tue, Jun 10, 2014 at 12:08 AM, Sebastian Lackner
<sebastian at fds-team.de> wrote:
> Thanks for all the feedback @ Ken, Daniel, Bruno and all the other
> people I talked to.
>
> Changes in try 3:
>
> * Although the fd_cache_epoch was slightly faster in my tests (-> see
> plots in mail for try 1) and should also work on PPC, its probably
> better to choose a method which is easier to verify, and where we can be
> sure, that it doesn't break with the next gcc release. ;) In this patch
> I switched back to the old approach using interlocked_cmpxchg64 to
> set/get both fd and associated attributes at the same time.
>
> * Although used in some other places, its probably better to avoid
> assert() for stuff, which should never be optimized away.

Just an update to my tests:
http://influenza.blog.br/wine/testpatch3.pdf

As expected it' slightly slower (Try 3 column), but still much better
than the current implementation and still under windows 7 measures in
my machine.

Best wishes,
Bruno