linux-kernel - RE: [PATCH 1/3] slub: set a criteria for slub node partial adding

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Date:	Wed, 14 Dec 2011 12:26:29 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
cc:	"Alex,Shi" <alex.shi@...el.com>,
	David Rientjes <rientjes@...gle.com>,
	"penberg@...nel.org" <penberg@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: RE: [PATCH 1/3] slub: set a criteria for slub node partial adding

On Wed, 14 Dec 2011, Eric Dumazet wrote:

> > Many people have done patchsets like this.
>
> Things changed a lot recently. There is room for improvements.
>
> At least we can exchange ideas _before_ coding a new patchset ?

Sure but I hope we do not simply rehash what has been said before and
recode what others have code in years past.

> > There are various permutations
> > on SL?B (I dont remember them all SLEB, SLXB, SLQB etc) that have been
> > proposed over the years. Caches tend to grow and get rather numerous (see
> > SLAB) and the design of SLUB was to counter that. There is a reason it was
> > called SLUB. The U stands for Unqueued and was intended to avoid the
> > excessive caching problems that I ended up when reworking SLAB for NUMA
> > support.
>
> Current 'one active slab' per cpu is a one level cache.
>
> It really is a _queue_ containing a fair amount of objects.

In some sense you are right. It is a set of objects linked together. That
can be called a queue and it has certain cache hot effects. It is not a
qeueue in the SLAB sense meaning a configurable array of pointers.

> My initial idea would be to use a cache of 4 slots per cpu, but be able
> to queue many objects per slot, if they all belong to same slab/page.

Nick did that. Please read up on his work. I think it was named SLQB.
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