From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752944Ab3L0GJx (ORCPT ); Fri, 27 Dec 2013 01:09:53 -0500 Received: from terminus.zytor.com ([198.137.202.10]:50491 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751639Ab3L0GJv (ORCPT ); Fri, 27 Dec 2013 01:09:51 -0500 Message-ID: <52BD199A.8070607@zytor.com> Date: Thu, 26 Dec 2013 22:09:30 -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 CC: Ingo Molnar , Thomas Gleixner , Al Viro , the arch/x86 maintainers , linux-fsdevel , Linux Kernel Mailing List Subject: Re: [RFC] speeding up the stat() family of system calls... References: <20131224204625.GB20471@gmail.com> 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 12/26/2013 11:00 AM, Linus Torvalds wrote: > > Interestingly, looking at the cp_new_stat() profiles, the games we > play to get efficient range checking seem to actually hurt us. Maybe > it's the "sbb" that is just expensive, or maybe it's turning a (very > predictable) conditional branch into a data dependency chain instead. > Or maybe it's just random noise in my profiles that happened to make > those sbb's look bad. > Much to my surprise, this patch adds almost 10K of text to an "allyesconfig" build. I wouldn't have expected it. I'll look at it some more tomorrow. -hpa