From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ob0-f182.google.com (mail-ob0-f182.google.com [209.85.214.182]) by kanga.kvack.org (Postfix) with ESMTP id 059036B003D for ; Tue, 1 Apr 2014 16:15:34 -0400 (EDT) Received: by mail-ob0-f182.google.com with SMTP id uz6so11698963obc.13 for ; Tue, 01 Apr 2014 13:15:34 -0700 (PDT) Received: from mail-oa0-x22c.google.com (mail-oa0-x22c.google.com [2607:f8b0:4003:c02::22c]) by mx.google.com with ESMTPS id i2si15894777oeu.174.2014.04.01.13.15.34 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 01 Apr 2014 13:15:34 -0700 (PDT) Received: by mail-oa0-f44.google.com with SMTP id n16so11829213oag.3 for ; Tue, 01 Apr 2014 13:15:34 -0700 (PDT) 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 Message-ID: Subject: Re: [PATCH] ipc,shm: increase default size for shmmax Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Kamezawa Hiroyuki , Davidlohr Bueso , Manfred Spraul , aswin@hp.com, LKML , "linux-mm@kvack.org" , "Gotou, Yasunori" , chenhanxiao , Gao feng >> 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org