From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261405AbUEKCOg (ORCPT ); Mon, 10 May 2004 22:14:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261468AbUEKCOg (ORCPT ); Mon, 10 May 2004 22:14:36 -0400 Received: from hera.kernel.org ([63.209.29.2]:61389 "EHLO hera.kernel.org") by vger.kernel.org with ESMTP id S261405AbUEKCOe (ORCPT ); Mon, 10 May 2004 22:14:34 -0400 To: linux-kernel@vger.kernel.org From: hpa@zytor.com (H. Peter Anvin) Subject: Re: AMD64 and RAID6 Date: Tue, 11 May 2004 02:13:47 +0000 (UTC) Organization: Transmeta Corporation, Santa Clara CA Message-ID: References: <409D1D86.6050907@clanhk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT X-Trace: terminus.zytor.com 1084241627 30863 127.0.0.1 (11 May 2004 02:13:47 GMT) X-Complaints-To: news@terminus.zytor.com NNTP-Posting-Date: Tue, 11 May 2004 02:13:47 +0000 (UTC) X-Newsreader: trn 4.0-test76 (Apr 2, 2001) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Followup to: <409D1D86.6050907@clanhk.org> By author: "J. Ryan Earl" In newsgroup: linux.dev.kernel > > I noticed the following in my dmesg: > > raid5: measuring checksumming speed > generic_sse: 6604.000 MB/sec > raid5: using function: generic_sse (6604.000 MB/sec) > raid6: int64x1 1847 MB/s > raid6: int64x2 2753 MB/s > raid6: int64x4 2878 MB/s > raid6: int64x8 1902 MB/s > raid6: sse2x1 1015 MB/s > raid6: sse2x2 1488 MB/s > raid6: sse2x4 1867 MB/s > raid6: using algorithm sse2x4 (1867 MB/s) > md: raid6 personality registered as nr 8 > md: md driver 0.90.0 MAX_MD_DEVS=256, MD_SB_DISKS=27 > > Why doesn't RAID6 use the int64x4 algorithm in this situation? What is > the motivation of setting the 'prefer field' on the sse algorithms and > not on the integer based algorithms? > The SSE algorithms are non-cache-polluting. This makes them slightly slower, but avoids slowing the rest of the machine down as much. -hpa