Return-Path: linux-nfs-owner@vger.kernel.org Received: from mail-ob0-f179.google.com ([209.85.214.179]:42775 "EHLO mail-ob0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751640Ab3IQEms convert rfc822-to-8bit (ORCPT ); Tue, 17 Sep 2013 00:42:48 -0400 Received: by mail-ob0-f179.google.com with SMTP id wn1so4598445obc.24 for ; Mon, 16 Sep 2013 21:42:48 -0700 (PDT) Date: Mon, 16 Sep 2013 14:44:53 -0500 From: Rob Landley Subject: Re: [RFC] extending splice for copy offloading To: Eric Wong Cc: Zach Brown , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org, Trond Myklebust , Bryan Schumaker , "Martin K. Petersen" , Jens Axboe , Mark Fasheh , Joel Becker References: <1378919210-10372-1-git-send-email-zab@redhat.com> <20130911211722.GA9725@dcvr.yhbt.net> In-Reply-To: <20130911211722.GA9725@dcvr.yhbt.net> (from normalperson@yhbt.net on Wed Sep 11 16:17:23 2013) Message-Id: <1379360693.1974.29@driftwood> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; DelSp=Yes; Format=Flowed Sender: linux-nfs-owner@vger.kernel.org List-ID: On 09/11/2013 04:17:23 PM, Eric Wong wrote: > Zach Brown wrote: > > Towards the end of that thread Eric Wong asked why we didn't just > > extend splice. I immediately replied with some dumb dismissive > > answer. Once I sat down and looked at it, though, it does make a > > lot of sense. So good job, Eric. +10 Dummie points for me. > > Thanks for revisiting that :> > > > Some things to talk about: > > - I really don't care about the naming here. If you do, holler. > > Exposing "DIRECT" to userspace now might confuse users into expecting > O_DIRECT behavior. I say this as an easily-confused user. > > In the future, perhaps O_DIRECT behavior can become per-splice > (instead > of just per-open) and can save SPLICE_F_DIRECT for that. > > > - We might want different flags for file-to-file splicing and > acceleration > > - We might want flags to require or forbid acceleration > > > - We might want to provide all these flags to sendfile, too > > Another syscall? I prefer not. Better to just maintain the sendfile > API as-is for compatibility reasons and nudge users towards splice. > > > Thoughts? Objections? > > I'll try to test/comment more in a week or two (not much time for > computing until then). Just a vague note that I've wanted to use splice implementing cp and patch and cat and so on in toybox, but couldn't because it needs a pipe. So I'm quite interested in moves to lift this restriction... Rob