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. > > Cheers, > > Dave. > > -- > Dave Chinner > david@xxxxxxxxxxxxx -- Milosz Tanski CTO 16 East 34th Street, 15th floor New York, NY 10016 p: 646-253-9055 e: milosz@xxxxxxxxx -- 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
