Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932475AbWAKS5v (ORCPT ); Wed, 11 Jan 2006 13:57:51 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932635AbWAKS5v (ORCPT ); Wed, 11 Jan 2006 13:57:51 -0500 Received: from mx.pathscale.com ([64.160.42.68]:42678 "EHLO mx.pathscale.com") by vger.kernel.org with ESMTP id S932475AbWAKS5u (ORCPT ); Wed, 11 Jan 2006 13:57:50 -0500 Subject: Re: [PATCH 1 of 3] Introduce __raw_memcpy_toio32 From: "Bryan O'Sullivan" To: Roland Dreier Cc: Andrew Morton , Sam Ravnborg , hch@infradead.org, linux-kernel@vger.kernel.org In-Reply-To: References: <1136909276.32183.28.camel@serpentine.pathscale.com> <20060110170722.GA3187@infradead.org> <1136915386.6294.8.camel@serpentine.pathscale.com> <20060110175131.GA5235@infradead.org> <1136915714.6294.10.camel@serpentine.pathscale.com> <20060110140557.41e85f7d.akpm@osdl.org> <1136932162.6294.31.camel@serpentine.pathscale.com> <20060110153257.1aac5370.akpm@osdl.org> <1137000032.11245.11.camel@camp4.serpentine.com> <20060111172216.GA18292@mars.ravnborg.org> <20060111093019.097d156a.akpm@osdl.org> <1137001400.11245.31.camel@camp4.serpentine.com> Content-Type: text/plain Date: Wed, 11 Jan 2006 10:57:45 -0800 Message-Id: <1137005865.11245.47.camel@camp4.serpentine.com> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 (2.2.3-2.fc4) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 625 Lines: 19 On Wed, 2006-01-11 at 10:49 -0800, Roland Dreier wrote: > Your current implementation is out-of-line, right? The memcpy32 routine is, but __raw_memcpy_toio32 simply calls it, so we have two jump/ret pairs instead of one. > I would be surprised if calling a function has any overhead on x86_64, > since the function call is a jump that can be predicted perfectly. Indeed.