From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932801Ab3LXAAr (ORCPT ); Mon, 23 Dec 2013 19:00:47 -0500 Received: from terminus.zytor.com ([198.137.202.10]:49278 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932500Ab3LXAAq (ORCPT ); Mon, 23 Dec 2013 19:00:46 -0500 Message-ID: <52B8CE99.2050608@zytor.com> Date: Mon, 23 Dec 2013 16:00:25 -0800 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: Linus Torvalds , Ingo Molnar , Thomas Gleixner , Al Viro CC: the arch/x86 maintainers , linux-fsdevel , Linux Kernel Mailing List Subject: Re: [RFC] speeding up the stat() family of system calls... References: In-Reply-To: X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/21/2013 12:27 PM, Linus Torvalds wrote: > > HOWEVER. On x86, doing an efficient field-at-a-time copy also requires > us to use put_user_try() and put_user_catch() in order to not have > tons of clac/stac instructions for the extended permission testing. > And the implementation of that was actually fairly non-optimal, so to > actually get the code I wanted, I had to change how that all worked > too, using "asm_volatile_goto()". > I guess I'm a bit puzzled... the current code should be just fine if everything is present, and do we really care about the performance if we actually have an error condition? I'm a bit concerned about the put_user_fail: label having uniqueness problem, which I know some versions of gcc at least get very noisy over. I like the overall approach, however. -hpa