Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752361AbaKKGoX (ORCPT ); Tue, 11 Nov 2014 01:44:23 -0500 Received: from ipmail04.adl6.internode.on.net ([150.101.137.141]:51868 "EHLO ipmail04.adl6.internode.on.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751398AbaKKGoV (ORCPT ); Tue, 11 Nov 2014 01:44:21 -0500 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AsglAMOvYVR5LbBUPGdsb2JhbABcgw6BLYI2hQewewaVLoVsBAICgRoXAQEBAQEGAQEBATg7hAMBAQQ6HCMQCAMYCSUPBSUDBxoTiEDMdgELIBiGIopbB4RLBZAOjhaBNYcBkjkpL4JLAQEB Date: Tue, 11 Nov 2014 17:44:17 +1100 From: Dave Chinner 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 Subject: Re: [PATCH v6 0/7] vfs: Non-blockling buffered fs read (page cache only) Message-ID: <20141111064417.GT23575@dastard> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@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 from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/