linux-kernel - Re: [patch 0/6] Per cpu structures for SLUB

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Message-Id: <20070827165126.a1a9846b.akpm@linux-foundation.org>
Date:	Mon, 27 Aug 2007 16:51:26 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Christoph Lameter <clameter@....com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Pekka Enberg <penberg@...helsinki.fi>
Subject: Re: [patch 0/6] Per cpu structures for SLUB

On Mon, 27 Aug 2007 11:50:10 -0700 (PDT)
Christoph Lameter <clameter@....com> wrote:

> On Fri, 24 Aug 2007, Andrew Morton wrote:
> 
> > I'm struggling a bit to understand these numbers.  Bigger is better, I
> > assume?  In what units are these numbers?
> 
> No less is better. These are cycle counts. Hmmm... We discussed these 
> cycle counts so much in the last week that I forgot to mention that.
> 
> > > Page allocator pass through
> > > ---------------------------
> > > There is a significant difference in the columns marked with a * because
> > > of the way that allocations for page sized objects are handled.
> > 
> > OK, but what happened to the third pair of columns (Concurrent Alloc,
> > Kmalloc) for 1024 and 2048-byte allocations?  They seem to have become
> > significantly slower?
> 
> There is a significant performance increase there. That is the main point 
> of the patch.
> 
> > Thanks for running the numbers, but it's still a bit hard to work out
> > whether these changes are an aggregate benefit?
> 
> There is a drawback because of the additional code introduced in the fast 
> path. However, the regular kmalloc case shows improvements throughout. 
> This is in particular of importance for SMP systems. We see an improvement 
> even for 2 processors.

umm, OK.  When you have time, could you please whizz up a clearer
changelog for this one?
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