Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932212AbWBWQ7t (ORCPT ); Thu, 23 Feb 2006 11:59:49 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932234AbWBWQ7t (ORCPT ); Thu, 23 Feb 2006 11:59:49 -0500 Received: from kanga.kvack.org ([66.96.29.28]:21888 "EHLO kanga.kvack.org") by vger.kernel.org with ESMTP id S932212AbWBWQ7s (ORCPT ); Thu, 23 Feb 2006 11:59:48 -0500 Date: Thu, 23 Feb 2006 11:54:44 -0500 From: Benjamin LaHaise To: Linus Torvalds Cc: Arjan van de Ven , Linux Kernel Mailing List , ak@suse.de, Andrew Morton , Ingo Molnar Subject: Re: Patch to reorder functions in the vmlinux to a defined order Message-ID: <20060223165444.GC27682@kvack.org> References: <1140700758.4672.51.camel@laptopd505.fenrus.org> <1140707358.4672.67.camel@laptopd505.fenrus.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1309 Lines: 24 On Thu, Feb 23, 2006 at 08:48:43AM -0800, Linus Torvalds wrote: > For example, on x86(-64), memcpy() is mostly inlined for the interesting > cases. That's not always so. Other architectures will have things like the > page copying and clearing as _the_ hottest functions. Same goes for > architecture-specific things like context switching etc, that have > different names on different architectures. On x86-64 the way gcc inlines memcpy() is rather broken, too. If the kernel is compiled with -Os instead of -O2, gcc seems to always use rep ; movs or rep ; stos, which is substantially slower (factor of 10 or more for some sizes -- a few parallel issued pipelined instructions vs tieing up the entire pipeline until the size of the move is known and dispatched) for small size data structures. Each instance fixed was worth a few percent on the P4 when looking at lmbench's af_unix component. -ben -- "Ladies and gentlemen, I'm sorry to interrupt, but the police are here and they've asked us to stop the party." Don't Email: . - 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/