Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754360Ab3IZVZM (ORCPT ); Thu, 26 Sep 2013 17:25:12 -0400 Received: from mx1.redhat.com ([209.132.183.28]:50335 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753957Ab3IZVZJ (ORCPT ); Thu, 26 Sep 2013 17:25:09 -0400 Message-ID: <5244A5E7.90808@redhat.com> Date: Thu, 26 Sep 2013 17:23:51 -0400 From: Ric Wheeler User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130805 Thunderbird/17.0.8 MIME-Version: 1.0 To: Miklos Szeredi CC: Zach Brown , "J. Bruce Fields" , Anna Schumaker , Kernel Mailing List , Linux-Fsdevel , "linux-nfs@vger.kernel.org" , Trond Myklebust , Bryan Schumaker , "Martin K. Petersen" , Jens Axboe , Mark Fasheh , Joel Becker , Eric Wong Subject: Re: [RFC] extending splice for copy offloading References: <1378919210-10372-1-git-send-email-zab@redhat.com> <20130925183828.GA30372@lenny.home.zabbo.net> <20130925190620.GB30372@lenny.home.zabbo.net> <20130925195526.GA18971@fieldses.org> <20130925210742.GG30372@lenny.home.zabbo.net> <20130926153359.GE704@fieldses.org> <20130926190611.GP30372@lenny.home.zabbo.net> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1499 Lines: 35 On 09/26/2013 03:53 PM, Miklos Szeredi wrote: > On Thu, Sep 26, 2013 at 9:06 PM, Zach Brown wrote: > >>> But I'm not sure it's worth the effort; 99% of the use of this >>> interface will be copying whole files. And for that perhaps we need a >>> different API, one which has been discussed some time ago: >>> asynchronous copyfile() returns immediately with a pollable event >>> descriptor indicating copy progress, and some way to cancel the copy. >>> And that can internally rely on ->direct_splice(), with appropriate >>> algorithms for determine the optimal chunk size. >> And perhaps we don't. Perhaps we can provide this much simpler >> data-plane interface that works well enough for most everyone and can >> avoid going down the async rat hole, yet again. > I think either buffering or async is needed to get good perforrmace > without too much complexity in the app (which is not good). Buffering > works quite well for regular I/O, so maybe its the way to go here as > well. > > Thanks, > Miklos > Buffering misses the whole point of the copy offload - the idea is *not* to read or write the actual data in the most interesting cases which offload the operation to a smart target device or file system. Regards, Ric -- 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/