linux-kernel - Re: [PATCH] ipc,shm: increase default size for shmmax

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Date:	Thu, 17 Apr 2014 18:41:19 +0200
From:	Manfred Spraul <manfred@...orfullife.com>
To:	Michael Kerrisk <mtk.manpages@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>
CC:	Davidlohr Bueso <davidlohr@...com>,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>, aswin@...com,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH] ipc,shm: increase default size for shmmax

On 04/17/2014 12:41 PM, Michael Kerrisk wrote:
> On Thu, Apr 17, 2014 at 12:46 AM, Andrew Morton
> <akpm@...ux-foundation.org> wrote:
>> On Sun, 13 Apr 2014 20:05:34 +0200 Manfred Spraul <manfred@...orfullife.com> wrote:
>>
>>> Hi Andrew,
>>>
>>> On 04/02/2014 12:08 AM, Andrew Morton wrote:
>>>> Well, I'm assuming 64GB==infinity. It *was* infinity in the RHEL5
>>>> timeframe, but infinity has since become larger so pickanumber.
>>> I think infinity is the right solution:
>>> The only common case where infinity is wrong would be Android - and
>>> Android disables sysv shm entirely.
>>>
>>> There are two patches:
>>> http://marc.info/?l=linux-kernel&m=139730332306185&q=raw
>>> http://marc.info/?l=linux-kernel&m=139727299800644&q=raw
>>>
>>> Could you apply one of them?
>>> I wrote the first one, thus I'm biased which one is better.
>> I like your patch because applying it might encourage you to send more
>> kernel patches - I miss the old days ;)
>>
>> But I do worry about disrupting existing systems so I like Davidlohr's
>> idea of making the change a no-op for people who are currently
>> explicitly setting shmmax and shmall.
> Agreed. It's hard to imagine situations where people might care
> nowadays, but there's no limits to people's insane inventiveness. Some
> people really might want to set an upper limit.
I don't understand that: neither patch has any impact after an explicit 
sysctl that overwrites shmmax.

>> In an ideal world, system administrators would review this change,
> And in the ideal world, patches such as this would CC
> linux-api@...r.kernel.org, as described in
> Documentation/SubmitChecklist, so that users who care about getting
> advance warning on API changes could be alerted and might even review
> and comment...
Good point.
Davidlohr: Your patch has an impact on shmctl(,IPC_INFO,).
Could you add that for v3?

I'll try to make a v2 (with your update to the uapi header file) tomorrow.

--
     Manfred
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