From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Chinner Subject: Re: [PATCH v6 0/7] vfs: Non-blockling buffered fs read (page cache only) Date: Tue, 11 Nov 2014 17:44:17 +1100 Message-ID: <20141111064417.GT23575@dastard> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: owner-linux-aio@kvack.org To: Milosz Tanski Cc: linux-kernel@vger.kernel.org, Christoph Hellwig , linux-fsdevel@vger.kernel.org, linux-aio@kvack.org, Mel Gorman , Volker Lendecke , Tejun Heo , Jeff Moyer , Theodore Ts'o , Al Viro , linux-api@vger.kernel.org, Michael Kerrisk , linux-arch@vger.kernel.org List-Id: linux-api@vger.kernel.org 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.... Cheers, Dave. -- Dave Chinner david@fromorbit.com -- To unsubscribe, send a message with 'unsubscribe linux-aio' in the body to majordomo@kvack.org. For more info on Linux AIO, see: http://www.kvack.org/aio/ Don't email: aart@kvack.org