Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262461AbTIBVjq (ORCPT ); Tue, 2 Sep 2003 17:39:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262372AbTIBVjq (ORCPT ); Tue, 2 Sep 2003 17:39:46 -0400 Received: from mail.jlokier.co.uk ([81.29.64.88]:57482 "EHLO mail.jlokier.co.uk") by vger.kernel.org with ESMTP id S262461AbTIBVjo (ORCPT ); Tue, 2 Sep 2003 17:39:44 -0400 Date: Tue, 2 Sep 2003 22:39:05 +0100 From: Jamie Lokier To: Kars de Jong Cc: Geert Uytterhoeven , Linux/m68k kernel mailing list , Linux Kernel Development Subject: Re: x86, ARM, PARISC, PPC, MIPS and Sparc folks please run this Message-ID: <20030902213905.GC16805@mail.jlokier.co.uk> References: <1062407310.13046.6.camel@laptop.locamation.com> <20030901100807.GB1903@mail.jlokier.co.uk> <1062535375.3501.11.camel@kars.perseus.home> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1062535375.3501.11.camel@kars.perseus.home> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1202 Lines: 30 Kars de Jong wrote: > And no, this board has no way of getting a better time resolution than > the 100 Hz tick timer either ;-) The coherency test is fine. That's just logic. The clock granularity got me wondering whether the timing measurement is meaningful on these machines. It's possible for the shared test to take 2000 microseconds and the unshared test to take 10 microseconds, and they can still show up as 10ms if they both cross a clock tick boundary. The minimum of 128 tests of each type is likely to report 0 until timing_loops is larger enough to make all 128 consistently almost 10ms, according to the timing when each test starts. Then as we only care if there is an approximately 2:1 ratio or more, it is fine. That depends on the timing of each test not being synchronised with the clock ticks, or when they are, that not affecting the result. I'm not sure, but I have a feeling that the random shuffle makes it ok. Hmm. -- Jamie - 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/