linux-kernel - Re: [PATCH 0/1] mm: Remove the SLAB allocator

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Message-ID: <20190410081618.GA25494@eros.localdomain>
Date:   Wed, 10 Apr 2019 18:16:18 +1000
From:   "Tobin C. Harding" <me@...in.cc>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     "Tobin C. Harding" <tobin@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Tejun Heo <tj@...nel.org>, Qian Cai <cai@....pw>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Mel Gorman <mgorman@...hsingularity.net>
Subject: Re: [PATCH 0/1] mm: Remove the SLAB allocator

On Wed, Apr 10, 2019 at 10:02:36AM +0200, Vlastimil Babka wrote:
> On 4/10/19 4:47 AM, Tobin C. Harding wrote:
> > Recently a 2 year old bug was found in the SLAB allocator that crashes
> > the kernel.  This seems to imply that not that many people are using the
> > SLAB allocator.
> 
> AFAIK that bug required CONFIG_DEBUG_SLAB_LEAK, not just SLAB. That
> seems to imply not that many people are using SLAB when debugging and
> yeah, SLUB has better debugging support. But I wouldn't dare to make the
> broader implication :)

Point noted.

> > Currently we have 3 slab allocators.  Two is company three is a crowd -
> > let's get rid of one. 
> > 
> >  - The SLUB allocator has been the default since 2.6.23
> 
> Yeah, with a sophisticated reasoning :)
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a0acd820807680d2ccc4ef3448387fcdbf152c73
> 
> >  - The SLOB allocator is kinda sexy.  Its only 664 LOC, the general
> >    design is outlined in KnR, and there is an optimisation taken from
> >    Knuth - say no more.
> > 
> > If you are using the SLAB allocator please speak now or forever hold your peace ...
> 
> FWIW, our enterprise kernel use it (latest is 4.12 based), and openSUSE
> kernels as well (with openSUSE Tumbleweed that includes latest
> kernel.org stables). AFAIK we don't enable SLAB_DEBUG even in general
> debug kernel flavours as it's just too slow.

Ok, so that probably already kills this.  Thanks for the response.  No
flaming, no swearing, man! and they said LKML was a harsh environment ...

> IIRC last time Mel evaluated switching to SLUB, it wasn't a clear
> winner, but I'll just CC him for details :)

Probably don't need to take up too much of Mel's time, if we have one
user in production we have to keep it, right.

Thanks for your time Vlastimil.


	Tobin