From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f51.google.com (mail-pa0-f51.google.com [209.85.220.51]) by kanga.kvack.org (Postfix) with ESMTP id 8EBBC6B013F for ; Wed, 2 Apr 2014 19:48:21 -0400 (EDT) Received: by mail-pa0-f51.google.com with SMTP id kq14so916388pab.24 for ; Wed, 02 Apr 2014 16:48:21 -0700 (PDT) Received: from fgwmail5.fujitsu.co.jp (fgwmail5.fujitsu.co.jp. [192.51.44.35]) by mx.google.com with ESMTPS id jh5si2095467pbb.426.2014.04.02.16.48.20 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Wed, 02 Apr 2014 16:48:20 -0700 (PDT) Received: from m1.gw.fujitsu.co.jp (unknown [10.0.50.71]) by fgwmail5.fujitsu.co.jp (Postfix) with ESMTP id 2BF623EE1D8 for ; Thu, 3 Apr 2014 08:48:19 +0900 (JST) Received: from smail (m1 [127.0.0.1]) by outgoing.m1.gw.fujitsu.co.jp (Postfix) with ESMTP id 1D4AA45DE54 for ; Thu, 3 Apr 2014 08:48:19 +0900 (JST) Received: from s1.gw.fujitsu.co.jp (s1.gw.nic.fujitsu.com [10.0.50.91]) by m1.gw.fujitsu.co.jp (Postfix) with ESMTP id 04D4745DE53 for ; Thu, 3 Apr 2014 08:48:19 +0900 (JST) Received: from s1.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s1.gw.fujitsu.co.jp (Postfix) with ESMTP id EAA551DB804A for ; Thu, 3 Apr 2014 08:48:18 +0900 (JST) Received: from m1000.s.css.fujitsu.com (m1000.s.css.fujitsu.com [10.240.81.136]) by s1.gw.fujitsu.co.jp (Postfix) with ESMTP id 9771D1DB803F for ; Thu, 3 Apr 2014 08:48:18 +0900 (JST) Message-ID: <533CA179.3050005@jp.fujitsu.com> Date: Thu, 03 Apr 2014 08:47:05 +0900 From: Kamezawa Hiroyuki MIME-Version: 1.0 Subject: Re: [PATCH] ipc,shm: increase default size for shmmax 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> <20140402155507.1d976144@alan.etchedpixels.co.uk> In-Reply-To: <20140402155507.1d976144@alan.etchedpixels.co.uk> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: One Thousand Gnomes , Andrew Morton Cc: Davidlohr Bueso , Manfred Spraul , aswin@hp.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, KOSAKI Motohiro , "Gotou, Yasunori" , chenhanxiao , Gao feng (2014/04/02 23:55), One Thousand Gnomes wrote: >> Why aren't people just setting the sysctl to a petabyte? What problems >> would that lead to? > > Historically - hanging on real world desktop systems when someone > accidentally creates a giant SHM segment and maps it. > > If you are running with vm overcmmit set to actually do checks then it > *shouldn't* blow up nowdays. > > More to the point wtf are people still using prehistoric sys5 IPC APIs > not shmemfs/posix shmem ? > AFAIK, there are many sys5 ipc users. And admins are using ipcs etc...for checking status. I guess they will not change the attitude until they see trouble with sysv IPC. *) I think some RedHat's document(MRG?) says sysv IPC is obsolete clearly but... I tend to recommend posix shared memory when people newly starts development but there is an another trap. IIUC, for posix shmem, an implicit size limit is applied by tmpfs's fs size. tmpfs mounted on /dev/shm tends to be limited to half size of system memory. It's hard to know that limit for users before hitting trouble. Thanks, -Kame -- 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 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933623AbaDBXsX (ORCPT ); Wed, 2 Apr 2014 19:48:23 -0400 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:43833 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932312AbaDBXsV (ORCPT ); Wed, 2 Apr 2014 19:48:21 -0400 X-SecurityPolicyCheck: OK by SHieldMailChecker v1.8.4 Message-ID: <533CA179.3050005@jp.fujitsu.com> Date: Thu, 03 Apr 2014 08:47:05 +0900 From: Kamezawa Hiroyuki User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: One Thousand Gnomes , Andrew Morton CC: Davidlohr Bueso , Manfred Spraul , aswin@hp.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, KOSAKI Motohiro , "Gotou, Yasunori" , chenhanxiao , Gao feng Subject: Re: [PATCH] ipc,shm: increase default size for shmmax 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> <20140402155507.1d976144@alan.etchedpixels.co.uk> In-Reply-To: <20140402155507.1d976144@alan.etchedpixels.co.uk> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (2014/04/02 23:55), One Thousand Gnomes wrote: >> Why aren't people just setting the sysctl to a petabyte? What problems >> would that lead to? > > Historically - hanging on real world desktop systems when someone > accidentally creates a giant SHM segment and maps it. > > If you are running with vm overcmmit set to actually do checks then it > *shouldn't* blow up nowdays. > > More to the point wtf are people still using prehistoric sys5 IPC APIs > not shmemfs/posix shmem ? > AFAIK, there are many sys5 ipc users. And admins are using ipcs etc...for checking status. I guess they will not change the attitude until they see trouble with sysv IPC. *) I think some RedHat's document(MRG?) says sysv IPC is obsolete clearly but... I tend to recommend posix shared memory when people newly starts development but there is an another trap. IIUC, for posix shmem, an implicit size limit is applied by tmpfs's fs size. tmpfs mounted on /dev/shm tends to be limited to half size of system memory. It's hard to know that limit for users before hitting trouble. Thanks, -Kame