linux-kernel - Re: [PATCH] atomic: add atomic_inc_not_zero

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Message-ID: <20101115140739.GJ7269@basil.fritz.box>
Date:	Mon, 15 Nov 2010 15:07:39 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Christoph Lameter <cl@...ux.com>
Cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Ingo Molnar <mingo@...e.hu>, Andi Kleen <andi@...stfloor.org>,
	Nick Piggin <npiggin@...nel.dk>
Subject: Re: [PATCH] atomic: add atomic_inc_not_zero_hint()

On Mon, Nov 15, 2010 at 07:57:10AM -0600, Christoph Lameter wrote:
> On Sat, 13 Nov 2010, Paul E. McKenney wrote:
> 
> > On Fri, Nov 12, 2010 at 01:14:12PM -0600, Christoph Lameter wrote:
> > >
> > > prefetchw() would be too much overhead?
> >
> > No idea.  Where do you believe that prefetchw() should be added?
> 
> It is another way to get an exclusive cache line
> for situations like this. No need to give a hint.

prefetchw doesn't work on Intel (or rather is equivalent to prefetch), 
for Intel you always need to explicitely write to get an exclusive
line.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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