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

From: Sebastian Frias <sf84@laposte.net>
To: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
Cc: "Austin S. Hemmelgarn" <ahferroin7@gmail.com>,
	Michal Hocko <mhocko@kernel.org>, Mason <slash.tmp@free.fr>,
	linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm: add config option to select the initial overcommit mode
Date: Fri, 13 May 2016 17:15:26 +0200	[thread overview]
Message-ID: <5735EF8E.4000707@laposte.net> (raw)
In-Reply-To: <20160513160142.2cc7d695@lxorguk.ukuu.org.uk>

Hi Alan,

On 05/13/2016 05:01 PM, One Thousand Gnomes wrote:
> On Fri, 13 May 2016 15:34:52 +0200
> Sebastian Frias <sf84@laposte.net> wrote:
> 
>> Hi Austin,
>>
>> On 05/13/2016 03:11 PM, Austin S. Hemmelgarn wrote:
>>> On 2016-05-13 08:39, Sebastian Frias wrote:  
>>>>
>>>> My point is that it seems to be possible to deal with such conditions in a more controlled way, ie: a way that is less random and less abrupt.  
>>> There's an option for the OOM-killer to just kill the allocating task instead of using the scoring heuristic.  This is about as deterministic as things can get though.  
>>
>> By the way, why does it has to "kill" anything in that case?
>> I mean, shouldn't it just tell the allocating task that there's not enough memory by letting malloc return NULL?
> 
> Just turn off overcommit and it will do that. With overcommit disabled
> the kernel will not hand out address space in excess of memory plus swap.

I think I'm confused.
Michal just said:

   "And again, overcommit=never doesn't imply no-OOM. It just makes it less
likely. The kernel can consume quite some unreclaimable memory as well."

which I understand as the OOM-killer will still lurk around and could still wake up.

Will overcommit=never totally disable the OOM-Killer or not?

Best regards,

Sebastian