[$] Buffered I/O without page-cache thrashing

Linux offers two modes for file I/O: buffered and direct. Buffered I/Opasses through the kernel's page cache; it is relatively easy to use andcan yield significant performance benefits for data that is accessedmultiple times. Direct I/O, instead, goes straight between a user-spacebuffer and the storage device. It can be much faster for situations wherecaching by the operating system isn't necessary, but it is complex to useand contains traps for the unwary. Now, it seems, Jens Axboe has come upwith away to get many of the benefits of direct I/O with a lot less bother.