Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753444AbWKGVlH (ORCPT ); Tue, 7 Nov 2006 16:41:07 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753442AbWKGVlH (ORCPT ); Tue, 7 Nov 2006 16:41:07 -0500 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:6413 "EHLO spitz.ucw.cz") by vger.kernel.org with ESMTP id S1753444AbWKGVlG (ORCPT ); Tue, 7 Nov 2006 16:41:06 -0500 Date: Tue, 7 Nov 2006 21:26:14 +0000 From: Pavel Machek To: Mikulas Patocka Cc: Albert Cahalan , linux-kernel@vger.kernel.org Subject: Re: 2048 CPUs [was: Re: New filesystem for Linux] Message-ID: <20061107212614.GA6730@ucw.cz> References: <787b0d920611041154l69db46abv4c8c467809ada57c@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1062 Lines: 33 Hi! > >The SGI Altix can have 2048 CPUs. > > And does it run one image of Linux? Or more images each > on few cpus? > > How do they solve problem with spinlock livelocks? > > If time-spent-outside-spinlock/time-spent-in-spinlock < > number-of-cpus, the spinlock livelock may happen --- > this condition is not true normally with 2 or 4 cpus, > but for that high amount of cpus, there is a danger. Lets say time-spent-outside-spinlock == time-spent-in-spinlock and number-of-cpus == 2. 1 < 2 , so it should livelock according to you... ...but afaict this should work okay. Even if spinlocks are very unfair, as long as time-outside and time-inside comes in big chunks, it should work. If you are unlucky, one cpu may stall for a while, but... I see no livelock. -- Thanks for all the (sleeping) penguins. - 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/