Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261806AbVASReW (ORCPT ); Wed, 19 Jan 2005 12:34:22 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261796AbVASRcy (ORCPT ); Wed, 19 Jan 2005 12:32:54 -0500 Received: from palrel10.hp.com ([156.153.255.245]:10131 "EHLO palrel10.hp.com") by vger.kernel.org with ESMTP id S261780AbVASRbI (ORCPT ); Wed, 19 Jan 2005 12:31:08 -0500 From: David Mosberger MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <16878.39257.133688.118974@napali.hpl.hp.com> Date: Wed, 19 Jan 2005 09:31:05 -0800 To: Nick Piggin Cc: davidm@hpl.hp.com, Linus Torvalds , "Luck, Tony" , linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: pipe performance regression on ia64 In-Reply-To: <41EE5601.7060700@yahoo.com.au> References: <200501181741.j0IHfGf30058@unix-os.sc.intel.com> <41ED9D06.1070301@yahoo.com.au> <16877.60406.192245.106565@napali.hpl.hp.com> <41EE5601.7060700@yahoo.com.au> X-Mailer: VM 7.19 under Emacs 21.3.1 Reply-To: davidm@hpl.hp.com X-URL: http://www.hpl.hp.com/personal/David_Mosberger/ Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1206 Lines: 25 >>>>> On Wed, 19 Jan 2005 23:43:45 +1100, Nick Piggin said: Nick> Oh that's quite true. A bad score on SMP on the pipe benchmark Nick> does not mean anything is broken. Nick> And IMO, probably many (most?) lmbench tests should be run Nick> with all processes bound to the same CPU on SMP systems to get Nick> the best repeatability and an indication of the basic serial Nick> speed of the operation (which AFAIK is what they aim to Nick> measure). We need to keep an eye on both the intra- and the inter-cpu pipe-bandwidth and should measure them explicitly. The problem is that at the moment, we get one, the other, or a mixture of the two, subject to the vagaries of the scheduler. If we could reliably measure both intra and inter-cpu cases, we may well find new optimization opportunities (I'm almost certain that's the case for the cross-cpu case; which is probably the more important case, actually). --david - 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/