From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753174AbbDAJjM (ORCPT ); Wed, 1 Apr 2015 05:39:12 -0400 Received: from mail.skyhub.de ([78.46.96.112]:39005 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752373AbbDAJjI (ORCPT ); Wed, 1 Apr 2015 05:39:08 -0400 Date: Wed, 1 Apr 2015 11:37:10 +0200 From: Borislav Petkov To: Frederic Weisbecker Cc: LKML , "Paul E . McKenney" Subject: Re: [PATCH 0/5] Support negative number of CPUs Message-ID: <20150401093709.GA18403@pd.tnic> References: <1427844036-1325-1-git-send-email-fweisbec@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1427844036-1325-1-git-send-email-fweisbec@gmail.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 01, 2015 at 01:20:31AM +0200, Frederic Weisbecker wrote: > Support for machines without any CPU at all was brought 3 years ago > by Paul (https://lkml.org/lkml/2012/3/31/131). The goal was to reduce > the complexity of programming on modern computing. > > Now meeting the simplicity beyond that of sequential programming had a > cost: such hardware configuration found a user base but didn't meet much > success among HPC users. > > So we have now a new challenge to solve: keep the beyond-sequential > programming simplicity while providing a highly parallel processing that > still scale. > > This patchset proposes a solution. The support for negative number of > CPUs is able to help scale computing up to O(-NR_CPUS). The more you have > CPUs the higher you scale, to the point that software execution should > complete before you start writing that software (assuming you have around > -1024 CPUs). And programming gets even more simple because you have lesser > CPUs to handle. > > Now keep in mind this patchset is only a draft. Not build tested and > I don't have the hardware yet. > > Frederic Weisbecker (5): > cpu: Infrastructure for negative cpu handling > smp: IPI handling for negative CPU > cpumask: Basic negative number of CPUs handling > init: Support negative CPUs boot and halt code > x86: Support reverse execution I have been wanting a feature like that since forever! Thanks for doing this Frederic. I'd like to propose an addition to that feature: execute whole programs backwards. But should be easily doable with patch 5 in the series. Acked-by: Borislav Petkov -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. --