Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752233AbaKKVkX (ORCPT ); Tue, 11 Nov 2014 16:40:23 -0500 Received: from ipmail04.adl6.internode.on.net ([150.101.137.141]:2939 "EHLO ipmail04.adl6.internode.on.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751741AbaKKVkR (ORCPT ); Tue, 11 Nov 2014 16:40:17 -0500 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AlRhAEiBYlR5LbBUPGdsb2JhbABcgw5UWYI2hQexDwIDBpNKgWWFbAICAQECgRkXAQEBAQEGAQEBATg7hAMBAQQ6HCMQCAMYCSUPBSUDBxoTiEDPNgELAR8YhiKKWgeESwWFIAKRYocggTWHAZI5KS+CSwEBAQ Date: Wed, 12 Nov 2014 08:40:12 +1100 From: Dave Chinner To: Milosz Tanski Cc: LKML , 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 , Michael Kerrisk , linux-arch@vger.kernel.org Subject: Re: [PATCH v6 0/7] vfs: Non-blockling buffered fs read (page cache only) Message-ID: <20141111214012.GU23575@dastard> References: <20141111064417.GT23575@dastard> 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 Tue, Nov 11, 2014 at 11:02:00AM -0500, Milosz Tanski wrote: > On Tue, Nov 11, 2014 at 1:44 AM, Dave Chinner 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@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/