linux-kernel - Re: [git pull] SLUB updates for 2.6.25

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Message-ID: <Pine.LNX.4.64.0802041542570.4774@schroedinger.engr.sgi.com>
Date:	Mon, 4 Feb 2008 15:47:36 -0800 (PST)
From:	Christoph Lameter <clameter@....com>
To:	Nick Piggin <nickpiggin@...oo.com.au>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [git pull] SLUB updates for 2.6.25

On Tue, 5 Feb 2008, Nick Piggin wrote:

> > erk, sorry, I misremembered.   I was about to merge all the patches we
> > weren't going to merge.  oops.
> 
> While you're there, can you drop the patch(es?) I commented on
> and didn't get an answer to. Like the ones that open code their
> own locking primitives and do risky looking things with barriers
> to boot...

That patch will be moved to a special archive for 
microbenchmarks. It shows the same issues like the __unlock patch.
 
> Also, WRT this one:
> slub-use-non-atomic-bit-unlock.patch
> 
> This is strange that it is unwanted. Avoiding atomic operations
> is a pretty good idea. The fact that it appears to be slower on
> some microbenchmark on some architecture IMO either means that
> their __clear_bit_unlock or the CPU isn't implemented so well...

Its slower on x86_64 and that is a pretty important arch. So 
I am to defer this until we have analyzed the situation some more. Could 
there be some effect of atomic ops on the speed with which a cacheline is 
released?

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