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Message-ID: <535237AA.7080000@colorfullife.com>
Date: Sat, 19 Apr 2014 10:45:30 +0200
From: Manfred Spraul <manfred@colorfullife.com>
MIME-Version: 1.0
Subject: Re: [PATCH] ipc/shm: Increase the defaults for SHMALL, SHMMAX to
 infinity
References: <1397812720-5629-1-git-send-email-manfred@colorfullife.com> <1397890512.19331.21.camel@buesod1.americas.hpqcorp.net> <CAKgNAkgMrWhSky8Cys2gxiS_s0=ya=wi=R5ehuT0bdjEBpDgdg@mail.gmail.com>
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To: mtk.manpages@gmail.com, Davidlohr Bueso <davidlohr@hp.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, Davidlohr Bueso <davidlohr.bueso@hp.com>, LKML <linux-kernel@vger.kernel.org>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>, KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>, Greg Thelen <gthelen@google.com>, aswin@hp.com, "linux-mm@kvack.org" <linux-mm@kvack.org>

On 04/19/2014 09:10 AM, Michael Kerrisk (man-pages) wrote:
> On Sat, Apr 19, 2014 at 8:55 AM, Davidlohr Bueso <davidlohr@hp.com> wrote:
>> On Fri, 2014-04-18 at 11:18 +0200, Manfred Spraul wrote:
>>> Risks:
>>> - The patch breaks installations that use "take current value and increase
>>>    it a bit". [seems to exist, http://marc.info/?l=linux-mm&m=139638334330127]
>> This really scares me. The probability of occurrence is now much higher,
>> and not just theoretical. It would legitimately break userspace.
> I'm missing something. Manfred's patch doesn't actually change the
> behavior on this point does it? If the problem is more than
> theoretical, then it _already_ affects users, right? (And they would
> therefore already be working around the problem.)
The current default is 32 MB. if some increases it by 1 MB, then the 
result is 33 MB.
The new default would be ULONG_MAX. If someone increases it by 1 MB, 
then the result is 1 MB - 1 byte.

--
     Manfred

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