On Tue, Nov 11, 2014 at 11:02:00AM -0500, Milosz Tanski wrote: > On Tue, Nov 11, 2014 at 1:44 AM, Dave Chinner <david@xxxxxxxxxxxxx> wrote: > > On Mon, Nov 10, 2014 at 11:40:23AM -0500, Milosz Tanski wrote: > >> This patcheset introduces an ability to perform a non-blocking read from > >> regular files in buffered IO mode. This works by only for those filesystems > >> that have data in the page cache. > >> > >> It does this by introducing new syscalls new syscalls preadv2/pwritev2. These > >> new syscalls behave like the network sendmsg, recvmsg syscalls that accept an > >> extra flag argument (RWF_NONBLOCK). > >> > >> It's a very common patern today (samba, libuv, etc..) use a large threadpool to > >> perform buffered IO operations. They submit the work form another thread > >> that performs network IO and epoll or other threads that perform CPU work. This > >> leads to increased latency for processing, esp. in the case of data that's > >> already cached in the page cache. > >> > >> With the new interface the applications will now be able to fetch the data in > >> their network / cpu bound thread(s) and only defer to a threadpool if it's not > >> there. In our own application (VLDB) we've observed a decrease in latency for > >> "fast" request by avoiding unnecessary queuing and having to swap out current > >> tasks in IO bound work threads. > > > > Can you write a test (or set of) for fstests that exercises this new > > functionality? I'm not worried about performance, just > > correctness.... > > Sure thing. Can you point me at the fstests repo? A quick google > search reveals lots of projects named fstests, most of them abandoned. git://git.kernel.org/pub/scm/fs/xfs/xfstests-dev.git Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
