Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1946860AbWKKAX5 (ORCPT ); Fri, 10 Nov 2006 19:23:57 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1946863AbWKKAX5 (ORCPT ); Fri, 10 Nov 2006 19:23:57 -0500 Received: from mail.suse.de ([195.135.220.2]:6850 "EHLO mx1.suse.de") by vger.kernel.org with ESMTP id S1946860AbWKKAX4 (ORCPT ); Fri, 10 Nov 2006 19:23:56 -0500 From: Andi Kleen To: "Bela Lubkin" Subject: Re: touch_cache() only touches two thirds Date: Sat, 11 Nov 2006 01:23:38 +0100 User-Agent: KMail/1.9.5 Cc: linux-kernel@vger.kernel.org, mingo@elte.hu References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200611110123.38309.ak@suse.de> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1488 Lines: 36 > The corrected code in > covers the full cache range. Granted that modern CPUs may be able to track > multiple simultaneous cache access streams: how many such streams are they > likely to be able to follow at once? It seems like going from 1 to 2 would > be a big win, 2 to 3 a small win, beyond that it wouldn't likely make much > incremental difference. So what do the actual implementations in the field > support? I remember reading at some point that a POWER4 could track at least 5+ parallel streams. I don't know how many K8 handles, but it is multiple too at least (forward and backwards) I don't have more data, but at least the newer Intel CPUs seem to be also very good at prefetching and when you look at a die photo the L/S unit in general is quite big. More than 6 streams handled is certainly a possibility. I guess it could be figured out with some clever benchmarking. > > The code (original and corrected) uses 6 simultaneous streams. My gut feeling is that this is not enough. > I have a modified version that takes a `ways' parameter to use an arbitrary > number of streams. I'll post that onto bugzilla.kernel.org. Post it to the list please. -Andi - 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/