Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752032AbaDAVsF (ORCPT ); Tue, 1 Apr 2014 17:48:05 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:38831 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751837AbaDAVsD (ORCPT ); Tue, 1 Apr 2014 17:48:03 -0400 Date: Tue, 1 Apr 2014 14:48:01 -0700 From: Andrew Morton To: KOSAKI Motohiro Cc: Davidlohr Bueso , Manfred Spraul , aswin@hp.com, LKML , "linux-mm@kvack.org" Subject: Re: [PATCH] ipc,shm: increase default size for shmmax Message-Id: <20140401144801.603c288674ab8f417b42a043@linux-foundation.org> In-Reply-To: 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> <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> X-Mailer: Sylpheed 3.2.0beta5 (GTK+ 2.24.10; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 1 Apr 2014 17:41:54 -0400 KOSAKI Motohiro wrote: > >> > Hmmm so 0 won't really work because it could be weirdly used to disable > >> > shm altogether... we cannot go to some negative value either since we're > >> > dealing with unsigned, and cutting the range in half could also hurt > >> > users that set the limit above that. So I was thinking of simply setting > >> > SHMMAX to ULONG_MAX and be done with it. Users can then set it manually > >> > if they want a smaller value. > >> > > >> > Makes sense? > >> > >> I don't think people use 0 for disabling. but ULONG_MAX make sense to me too. > > > > Distros could have set it to [U]LONG_MAX in initscripts ten years ago > > - less phone calls, happier customers. And they could do so today. > > > > But they haven't. What are the risks of doing this? > > I have no idea really. But at least I'm sure current default is much worse. > > 1. Solaris changed the default to total-memory/4 since Solaris 10 for DB. > http://www.postgresql.org/docs/9.1/static/kernel-resources.html > > 2. RHEL changed the default to very big size since RHEL5 (now it is > 64GB). Even tough many box don't have 64GB memory at that time. Ah-hah, that's interesting info. Let's make the default 64GB? Then we can blame RH if something goes wrong ;) -- 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/