Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753434AbaDCTCc (ORCPT ); Thu, 3 Apr 2014 15:02:32 -0400 Received: from mail-wi0-f179.google.com ([209.85.212.179]:45271 "EHLO mail-wi0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753258AbaDCTC2 (ORCPT ); Thu, 3 Apr 2014 15:02:28 -0400 Message-ID: <533DB03D.7010308@colorfullife.com> Date: Thu, 03 Apr 2014 21:02:21 +0200 From: Manfred Spraul User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.3.0 MIME-Version: 1.0 To: Davidlohr Bueso , KOSAKI Motohiro CC: Andrew Morton , aswin@hp.com, LKML , "linux-mm@kvack.org" , Greg Thelen , Kamezawa Hiroyuki Subject: Re: [PATCH] ipc,shm: disable shmmax and shmall by default References: <1396235199.2507.2.camel@buesod1.americas.hpqcorp.net> <20140331170546.3b3e72f0.akpm@linux-foundation.org> <1396371699.25314.11.camel@buesod1.americas.hpqcorp.net> <1396377083.25314.17.camel@buesod1.americas.hpqcorp.net> <1396386062.25314.24.camel@buesod1.americas.hpqcorp.net> <20140401142947.927642a408d84df27d581e36@linux-foundation.org> <20140401144801.603c288674ab8f417b42a043@linux-foundation.org> <1396394931.25314.34.camel@buesod1.americas.hpqcorp.net> <1396484447.2953.1.camel@buesod1.americas.hpqcorp.net> In-Reply-To: <1396484447.2953.1.camel@buesod1.americas.hpqcorp.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Davidlohr, On 04/03/2014 02:20 AM, Davidlohr Bueso wrote: > The default size for shmmax is, and always has been, 32Mb. > Today, in the XXI century, it seems that this value is rather small, > making users have to increase it via sysctl, which can cause > unnecessary work and userspace application workarounds[1]. > > Instead of choosing yet another arbitrary value, larger than 32Mb, > this patch disables the use of both shmmax and shmall by default, > allowing users to create segments of unlimited sizes. Users and > applications that already explicitly set these values through sysctl > are left untouched, and thus does not change any of the behavior. > > So a value of 0 bytes or pages, for shmmax and shmall, respectively, > implies unlimited memory, as opposed to disabling sysv shared memory. > This is safe as 0 cannot possibly be used previously as SHMMIN is > hardcoded to 1 and cannot be modified. Are we sure that no user space apps uses shmctl(IPC_INFO) and prints a pretty error message if shmall is too small? We would break these apps. -- Manfred -- 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/