From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754797AbaIPSYe (ORCPT ); Tue, 16 Sep 2014 14:24:34 -0400 Received: from tetsuo.zabbo.net ([50.193.208.193]:46073 "EHLO tetsuo.zabbo.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753000AbaIPSYc (ORCPT ); Tue, 16 Sep 2014 14:24:32 -0400 Date: Tue, 16 Sep 2014 11:24:31 -0700 From: Zach Brown To: "Elliott, Robert (Server Storage)" Cc: Andreas Dilger , Milosz Tanski , "linux-kernel@vger.kernel.org" , Christoph Hellwig , "linux-fsdevel@vger.kernel.org" , "linux-aio@kvack.org" , Mel Gorman , Volker Lendecke , Tejun Heo , Jeff Moyer Subject: Re: [RFC PATCH 0/7] Non-blockling buffered fs read (page cache only) Message-ID: <20140916182431.GJ19090@lenny.home.zabbo.net> References: <8EC2A7F3-0E25-4054-9863-4488B8ED5C8D@dilger.ca> <94D0CD8314A33A4D9D801C0FE68B402958C81D56@G9W0745.americas.hpqcorp.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <94D0CD8314A33A4D9D801C0FE68B402958C81D56@G9W0745.americas.hpqcorp.net> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 15, 2014 at 10:36:46PM +0000, Elliott, Robert (Server Storage) wrote: > > > > -----Original Message----- > > From: linux-kernel-owner@vger.kernel.org [mailto:linux-kernel- > > owner@vger.kernel.org] On Behalf Of Andreas Dilger > > Sent: Monday, 15 September, 2014 4:34 PM > > 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 > > Subject: Re: [RFC PATCH 0/7] Non-blockling buffered fs read (page cache only) > > > > On Sep 15, 2014, at 2:20 PM, 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 readv2/writev2 > > > and preadv2/pwritev2. These new syscalls behave like the network sendmsg, > > > recvmsg syscalls that accept an extra flag argument (O_NONBLOCK). > > > > It's too bad that we are introducing yet another new read/write > > syscall pair that only allow IO into discontiguous memory regions, > > but do not allow a single call to access discontiguous file regions > > (i.e. specify a separate file offset for each iov). > > > > Adding syscalls similar to preadv/pwritev() that could take a iovec > > that specified the file offset+length in addition to the memory address > > would allow efficient scatter-gather IO in a single syscall. While > > that is less critical for local filesystems with small syscall latency, > > it is more important for network filesystems, or in the case of > > NVRAM-backed filesystems. > > > > Cheers, Andreas > > That sounds like the proposed WRITE SCATTERED/READ GATHERED > commands for SCSI (where are related to, but not necessarily > tied to, atomic writes). We discussed them a bit at > LSF-MM 2013 - see http://lwn.net/Articles/548116/. It's the old {read,write}x proposals: http://www.mcs.anl.gov/uploads/cels/papers/TM-302-FINAL.pdf - z