Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 25 Jun 2002 13:05:02 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 25 Jun 2002 13:05:01 -0400 Received: from parcelfarce.linux.theplanet.co.uk ([195.92.249.252]:58886 "EHLO www.linux.org.uk") by vger.kernel.org with ESMTP id ; Tue, 25 Jun 2002 13:05:01 -0400 Message-ID: <3D18A26A.73E6DD07@zip.com.au> Date: Tue, 25 Jun 2002 10:03:38 -0700 From: Andrew Morton X-Mailer: Mozilla 4.79 [en] (X11; U; Linux 2.4.19-pre8 i686) X-Accept-Language: en MIME-Version: 1.0 To: Mala Anand CC: Linux Kernel Mailing List , lse-tech@lists.sourceforge.net Subject: Re: efficient copy_to_user and copy_from_user routines in Linux Kernel References: Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1078 Lines: 30 Mala Anand wrote: > > Here is a 2.5.19 patch that improves the performance of IA32 copy_to_user > and copy_from_user routines used by : > > (1) tcpip protocol stack > (2) file systems > This came up about a year back when zerocopy networking was merged. Intel boxes started running more slowly purely because of the 8+8 alignment thing. I changed tcp to use a different copy if either source or dest were not eight-byte aligned, and found that the resulting improvement across a mixed networking load was only 1%. Your numbers are higher, so perhaps there are different alignments in the mix... One question: have you tested on other CPU types? This problem is very specific to Intel hardware. On AMD, the eight-byte alignement artifact does not exist at all. It could be that your patch is not desirable on such CPUs? - - 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/