From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753863AbaIHNAz (ORCPT ); Mon, 8 Sep 2014 09:00:55 -0400 Received: from mout.kundenserver.de ([212.227.17.13]:56823 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753184AbaIHNAy (ORCPT ); Mon, 8 Sep 2014 09:00:54 -0400 From: Arnd Bergmann To: linux-arm-kernel@lists.infradead.org Cc: Robert Richter , Catalin Marinas , Will Deacon , Robert Richter , Mark Rutland , Radha Mohan Chintakuntla , linux-kernel@vger.kernel.org Subject: Re: [PATCH] arm64, defconfig: Increase NR_CPUS default to 64 Date: Mon, 08 Sep 2014 15:00:47 +0200 Message-ID: <3450151.nDuN2aF2Xl@wuerfel> User-Agent: KMail/4.11.5 (Linux/3.16.0-10-generic; KDE/4.11.5; x86_64; ; ) In-Reply-To: <1410176689-20020-1-git-send-email-rric@kernel.org> References: <1410176689-20020-1-git-send-email-rric@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Provags-ID: V02:K0:t7uZO6sR6Gh2/KhnpdZFruQ4ww78XuZAvPvdpfDbwi0 tGL7UXXo9YZCbRt6HmJd2WI3PKE6SIpXSfe64oQnJJbNIBaRtU zVqa7na2DveSIOHxrWyorO4IIfkVLsqWhIzsRkSIJOzEZm9B1H 6mcN/Ac2rQUYvmK8phCU1/XfyQrlv5Wd/iLx+D+WA/1/ONZs9c oMQhM5z+bGACgYu5HxbtaXNhNw5zxFR4frqobu8mvWSOwjhTB2 Tp0tmZaJZsN+qYCcsu7vMJiY4aW0tfB/3cqbuDwkD4/2XCRgmX iUAk5o4l/7vxo81cu3XcLZ+HMFZgUbWky5/1/4b4WRKa3IXv6j om7C30YK8Sz0weefs4jw= X-UI-Out-Filterresults: notjunk:1; Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Monday 08 September 2014 13:44:48 Robert Richter wrote: > From: Robert Richter > > Raising the current maximum limit to 64. This is needed for Cavium's > Thunder systems that will have at least 48 cores per die. > > The change keeps the current memory footprint in cpu mask structures. > It does not break existing code. Setting the maximum to 64 cpus still > boots systems with less cpus. > > Mark's Juno happily booted with a NR_CPUS=64 kernel. > > Tested on our Thunder system with 48 cores. We could see interrupts to > all cores. > > Cc: Radha Mohan Chintakuntla > Cc: Mark Rutland > Signed-off-by: Robert Richter > Acked-by: Arnd Bergmann FWIW, have you tried what happens when you increase the number further? We have architectures on which we support thousands of CPUs, so I wonder if there is a point at which this stops working on ARM64. Are you able to compile and boot a kernel built with e.g. NR_CPUS=256 or 4096 on your hardware? Arnd