From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964934AbXCSAYy (ORCPT ); Sun, 18 Mar 2007 20:24:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964959AbXCSAYy (ORCPT ); Sun, 18 Mar 2007 20:24:54 -0400 Received: from x35.xmailserver.org ([64.71.152.41]:50630 "EHLO x35.xmailserver.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964934AbXCSAYy (ORCPT ); Sun, 18 Mar 2007 20:24:54 -0400 X-AuthUser: davidel@xmailserver.org Date: Sun, 18 Mar 2007 17:22:48 -0700 (PDT) From: Davide Libenzi X-X-Sender: davide@alien.or.mcafeemobile.com To: Arnd Bergmann cc: Linux Kernel Mailing List , Andrew Morton , Linus Torvalds , Oleg Nesterov Subject: Re: [patch 2/13] signal/timer/event fds v6 - signalfd core ... In-Reply-To: <200703190045.24605.arnd@arndb.de> Message-ID: References: <200703172235.09227.arnd@arndb.de> <200703190045.24605.arnd@arndb.de> X-GPG-FINGRPRINT: CFAE 5BEE FD36 F65E E640 56FE 0974 BF23 270F 474E X-GPG-PUBLIC_KEY: http://www.xmailserver.org/davidel.asc MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 19 Mar 2007, Arnd Bergmann wrote: > On Sunday 18 March 2007, Davide Libenzi wrote: > > bah, __put_user is basically a move, so I don't think that efficency would > > be that different (assuming that it'd matter in this case). The only thing > > many __put_user do, is increase the exception table sizes. > > The cost of user access functions varies a lot depending on the > architectures. Those platforms with a 4G/4G split e.g. need to do more > than a simple move, and for s390 it may even come down to an indirect > function call, which incurs significant register pressure. Heh, I'd like ppl to agree on this, because I clearly remember in having an argoument with Andrew for the same thing, where I was doing stack setup plus copy_to_user() ;) - Davide