linux-kernel - Re: [PATCH] mm: add config option to select the initial overcommit mode

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Date:	Fri, 13 May 2016 13:01:25 -0400
From:	"Austin S. Hemmelgarn" <ahferroin7@...il.com>
To:	Sebastian Frias <sf84@...oste.net>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Michal Hocko <mhocko@...nel.org>
Cc:	Mason <slash.tmp@...e.fr>, linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: add config option to select the initial overcommit
 mode

On 2016-05-13 11:37, Sebastian Frias wrote:
> Hi Alan,
>
> On 05/13/2016 05:04 PM, One Thousand Gnomes wrote:
>>>> Perhaps Sebastian's choice could be made to depend on CONFIG_EMBEDDED,
>>>> rather than CONFIG_EXPERT?
>>>
>>> Even if the overcommit behavior is different on those systems the
>>> primary question hasn't been answered yet. Why cannot this be done from
>>> the userspace? In other words what wouldn't work properly?
>>
>> Most allocations in C have no mechanism to report failure.
>>
>> Stakc expansion failure is not reportable. Copy on write failure is not
>> reportable and so on.
>
> But wouldn't those affect a given process at at time?
> Does that means that the OOM-killer is woken up to kill process X when those situations arise on process Y?
Barring memory cgroups, if you have hit an OOM condition, it impacts the 
entire system.  Some process other than the one which first hit the 
failure may get killed, but every process will fail allocations until 
the situation is resolved.