Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753358AbYJFDn2 (ORCPT ); Sun, 5 Oct 2008 23:43:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752389AbYJFDnT (ORCPT ); Sun, 5 Oct 2008 23:43:19 -0400 Received: from mx1.redhat.com ([66.187.233.31]:55896 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751835AbYJFDnS (ORCPT ); Sun, 5 Oct 2008 23:43:18 -0400 Date: Sun, 5 Oct 2008 23:42:58 -0400 (EDT) From: Mikulas Patocka X-X-Sender: mpatocka@hs20-bc2-1.build.redhat.com To: david@lang.hm cc: Nick Piggin , Andrew Morton , linux-kernel@vger.kernel.org, agk@redhat.com, mbroz@redhat.com, chris@arachsys.com Subject: Re: application syncing options (was Re: [PATCH] Memory management livelock) In-Reply-To: Message-ID: References: <20080911101616.GA24064@agk.fab.redhat.com> <20080923154905.50d4b0fa.akpm@linux-foundation.org> <200810031232.23836.nickpiggin@yahoo.com.au> <200810031254.29121.nickpiggin@yahoo.com.au> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1682 Lines: 40 On Sun, 5 Oct 2008, david@lang.hm wrote: > On Sun, 5 Oct 2008, Mikulas Patocka wrote: > > > On Fri, 3 Oct 2008, david@lang.hm wrote: > > > > > I've also seen discussions of how the > > > kernel filesystem code can do ordered writes without having to wait for > > > them > > > with the use of barriers, is this capability exported to userspace? if so, > > > could you point me at documentation for it? > > > > It isn't. And it is good that it isn't --- the more complicated API, the > > more maintenance work. > > I can understand that most software would not want to deal with complications > like this, but for things thta have requirements similar to journaling > filesystems (databases for example) it would seem that there would be > advantages to exposing this capabilities. > > David Lang If you invent new interface that allows submitting several ordered IOs from userspace, it will require excessive maintenance overhead over long period of time. So it should be only justified, if the performance improvement is excessive as well. It should not be like "here you improve 10% performance on some synthetic benchmark in one application that was rewritten to support the new interface" and then create a few more security vulnerabilities (because of the complexity of the interface) and damage overall Linux progress, because everyone is catching bugs in the new interface and checking it for correctness. Mikulas -- 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/