linux-kernel - Re: [PATCH 16/16] mm/slab: introduce new slab management type, OBJFREELIST

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Message-ID: <alpine.DEB.2.20.1601271047480.14468@east.gentwo.org>
Date:	Wed, 27 Jan 2016 10:48:47 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	Vlastimil Babka <vbabka@...e.cz>
cc:	Joonsoo Kim <js1304@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Jesper Dangaard Brouer <brouer@...hat.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 16/16] mm/slab: introduce new slab management type,
 OBJFREELIST_SLAB

On Wed, 27 Jan 2016, Vlastimil Babka wrote:

> On 01/14/2016 06:24 AM, Joonsoo Kim wrote:
> > In fact, I tested another idea implementing OBJFREELIST_SLAB with
> > extendable linked array through another freed object. It can remove
> > memory waste completely but it causes more computational overhead
> > in critical lock path and it seems that overhead outweigh benefit.
> > So, this patch doesn't include it.
>
> Can you elaborate? Do we actually need an extendable linked array? Why not just
> store the pointer to the next free object into the object, NULL for the last
> one? I.e. a singly-linked list. We should never need to actually traverse it?
>
> freeing object obj:
> *obj = page->freelist;
> page->freelist = obj;
>
> allocating object:
> obj = page->freelist;
> page->freelist = *obj;
> *obj = NULL;

Well the single linked lists are a concept of another slab allocator. At
what point do we rename SLAB to SLUB2?