From mboxrd@z Thu Jan 1 00:00:00 1970 From: Manfred Spraul Subject: Re: [PATCH] IPC initialize shmmax and shmall from the current value not the default Date: Sun, 04 May 2014 13:17:40 +0200 Message-ID: <536621D4.60002@colorfullife.com> References: <5365723D.7030303@1h.com> <1399161216.2573.9.camel@buesod1.americas.hpqcorp.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1399161216.2573.9.camel-5JQ4ckphU/8SZAcGdq5asR6epYMZPwEe5NbjCUgZEJk@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Davidlohr Bueso , Marian Marinov Cc: Greg KH , akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, Linux Containers , n-horiguchi-PaJj6Psr51x8UrSeD/g0lQ@public.gmane.org, "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: containers.vger.kernel.org Hi Marian, Note: The limits will soon be increased to (nearly) ULONG_MAX. I.e.: If you propose the patch because you are running into issues with a too small SEMMAX after an unshare(CLONE_NEWIPC), then this will be fixed soon. On 05/04/2014 01:53 AM, Davidlohr Bueso wrote: > On Sun, 2014-05-04 at 01:48 +0300, Marian Marinov wrote: >> When we are creating new IPC namespace that should be cloned from the current namespace it is a good idea to copy the >> values of the current shmmax and shmall to the new namespace. The idea sounds reasonable: If an admin has reduced the limits, then the reduction should also apply after a unshare(CLONE_NEWIPC). But: Your patch doesn't use the current shmmax, it uses the shmmax from init_ipc_ns. Would it be possible to use the current values? > Why is this a good idea? > > This would break userspace that relies on the current behavior. > Furthermore we've recently changed the default value of both these > limits to be as large as you can get, thus deprecating them. I don't > like the idea of this being replaced by namespaces. Davidlohr: We are not deprecating them, we make the default huge. The limits should stay as usable as they were. With regards to breaking user space, I must think about it a bit more. Right now, each new namespace starts with SEMMAX=32MB, i.e. an often unusable default. -- Manfred