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Date:   Wed, 10 Apr 2019 14:53:34 -0700 (PDT)
From:   David Rientjes <rientjes@google.com>
To:     Vlastimil Babka <vbabka@suse.cz>
cc:     "Tobin C. Harding" <tobin@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Christoph Lameter <cl@linux.com>,
        Pekka Enberg <penberg@kernel.org>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Tejun Heo <tj@kernel.org>, Qian Cai <cai@lca.pw>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Mel Gorman <mgorman@techsingularity.net>
Subject: Re: [PATCH 0/1] mm: Remove the SLAB allocator
In-Reply-To: <f06aaeae-28c0-9ea4-d795-418ec3362d17@suse.cz>
Message-ID: <alpine.DEB.2.21.1904101452340.100430@chino.kir.corp.google.com>
References: <20190410024714.26607-1-tobin@kernel.org> <f06aaeae-28c0-9ea4-d795-418ec3362d17@suse.cz>
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On Wed, 10 Apr 2019, 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 :)
> 
> > 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.
> 
> IIRC last time Mel evaluated switching to SLUB, it wasn't a clear
> winner, but I'll just CC him for details :)
> 

We also use CONFIG_SLAB and disable CONFIG_SLAB_DEBUG for the same reason.