Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751707AbaDAUPg (ORCPT ); Tue, 1 Apr 2014 16:15:36 -0400 Received: from mail-oa0-f42.google.com ([209.85.219.42]:40872 "EHLO mail-oa0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751438AbaDAUPe (ORCPT ); Tue, 1 Apr 2014 16:15:34 -0400 MIME-Version: 1.0 In-Reply-To: <20140401121920.50d1dd96c2145acc81561b82@linux-foundation.org> References: <1396235199.2507.2.camel@buesod1.americas.hpqcorp.net> <20140331143217.c6ff958e1fd9944d78507418@linux-foundation.org> <1396306773.18499.22.camel@buesod1.americas.hpqcorp.net> <20140331161308.6510381345cb9a1b419d5ec0@linux-foundation.org> <1396308332.18499.25.camel@buesod1.americas.hpqcorp.net> <20140331170546.3b3e72f0.akpm@linux-foundation.org> <533A5CB1.1@jp.fujitsu.com> <20140401121920.50d1dd96c2145acc81561b82@linux-foundation.org> From: KOSAKI Motohiro Date: Tue, 1 Apr 2014 16:15:14 -0400 X-Google-Sender-Auth: VIFFC1amVq3JKJHg5EmeXfV3RtQ Message-ID: Subject: Re: [PATCH] ipc,shm: increase default size for shmmax To: Andrew Morton Cc: Kamezawa Hiroyuki , Davidlohr Bueso , Manfred Spraul , aswin@hp.com, LKML , "linux-mm@kvack.org" , "Gotou, Yasunori" , chenhanxiao , Gao feng Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >> Our middleware engineers has been complaining about this sysctl limit. >> System administrator need to calculate required sysctl value by making sum >> of all planned middlewares, and middleware provider needs to write "please >> calculate systcl param by....." in their installation manuals. > > Why aren't people just setting the sysctl to a petabyte? What problems > would that lead to? I don't have much Fujitsu middleware knowledges. But I'd like to explain very funny bug I saw. 1. middleware-A suggest to set SHMMAX to very large value (maybe LONG_MAX, but my memory was flushed) 2. middleware-B suggest to set SHMMAX to increase some dozen mega byte. Finally, it was overflow and didn't work at all. Let's demonstrate. # echo 18446744073709551615 > /proc/sys/kernel/shmmax # cat /proc/sys/kernel/shmmax 18446744073709551615 # echo 18446744073709551616 > /proc/sys/kernel/shmmax # cat /proc/sys/kernel/shmmax 0 That's why many open source software continue the silly game. But again, I don't have knowledge about Fujitsu middleware. I'm waiting kamezawa-san's answer. -- 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/