linux-kernel - Re: [PATCH 4.20 71/92] Revert "mm: slowly shrink slabs with a relatively small number of objects"

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Date:   Mon, 18 Feb 2019 19:30:53 +0000
From:   Roman Gushchin <guro@...com>
To:     Michal Hocko <mhocko@...nel.org>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rik van Riel <riel@...riel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        Dave Chinner <dchinner@...hat.com>,
        Wolfgang Walter <linux@...m.de>, Spock <dairinin@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 4.20 71/92] Revert "mm: slowly shrink slabs with a
 relatively small number of objects"

Ok, I’ll send the proposal later today.

Thanks!

Sent from my iPhone

> On Feb 18, 2019, at 11:14, Michal Hocko <mhocko@...nel.org> wrote:
> 
>> On Mon 18-02-19 18:57:45, Roman Gushchin wrote:
>>> On Mon, Feb 18, 2019 at 06:38:25PM +0100, Michal Hocko wrote:
>>>> On Mon 18-02-19 17:16:34, Greg KH wrote:
>>>>> On Mon, Feb 18, 2019 at 10:30:44AM -0500, Rik van Riel wrote:
>>>>>> On Mon, 2019-02-18 at 14:43 +0100, Greg Kroah-Hartman wrote:
>>>>>> 4.20-stable review patch.  If anyone has any objections, please let
>>>>>> me know.
>>>>>> 
>>>>>> ------------------
>>>>>> 
>>>>>> From: Dave Chinner <dchinner@...hat.com>
>>>>>> 
>>>>>> commit a9a238e83fbb0df31c3b9b67003f8f9d1d1b6c96 upstream.
>>>>>> 
>>>>>> This reverts commit 172b06c32b9497 ("mm: slowly shrink slabs with a
>>>>>> relatively small number of objects").
>>>>> 
>>>>> This revert will result in the slab caches of dead
>>>>> cgroups with a small number of remaining objects never
>>>>> getting reclaimed, which can be a memory leak in some
>>>>> configurations.
>>>>> 
>>>>> But hey, that's your tradeoff to make.
>>>> 
>>>> That's what is in Linus's tree.  Should we somehow diverge from that?
>>> 
>>> I believe we should start working on a memcg specific solution to
>>> minimize regressions for others and start a more complex solution from
>>> there.
>>> 
>>> Can we special case dead memcgs in the slab reclaim and reclaim more
>>> aggressively?
>> 
>> It's probably better to start a new thread to discuss this issue
> 
> agreed
> 
>> (btw, doesn't LSF/MM looks like the best place to do it? I can send a proposal).
> 
> I was about to do that if nobody else did.
> 
> dropped the rest of the email because this really deserves a new
> discussion.
> -- 
> Michal Hocko
> SUSE Labs