Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751924AbaDAV3w (ORCPT ); Tue, 1 Apr 2014 17:29:52 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:38638 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751886AbaDAV3t (ORCPT ); Tue, 1 Apr 2014 17:29:49 -0400 Date: Tue, 1 Apr 2014 14:29:47 -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: <20140401142947.927642a408d84df27d581e36@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> 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 17:12:50 -0400 KOSAKI Motohiro wrote: > On Tue, Apr 1, 2014 at 5:01 PM, Davidlohr Bueso wrote: > > On Tue, 2014-04-01 at 15:51 -0400, KOSAKI Motohiro wrote: > >> >> So, I personally like 0 byte per default. > >> > > >> > If by this you mean 0 bytes == unlimited, then I agree. It's less harsh > >> > then removing it entirely. So instead of removing the limit we can just > >> > set it by default to 0, and in newseg() if shm_ctlmax == 0 then we don't > >> > return EINVAL if the passed size is great (obviously), otherwise, if the > >> > user _explicitly_ set it via sysctl then we respect that. Andrew, do you > >> > agree with this? If so I'll send a patch. > >> > >> Yes, my 0 bytes mean unlimited. I totally agree we shouldn't remove the knob > >> entirely. > > > > 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? -- 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/