netdev - Re: iptables very slow after commit 784544739a25c30637397ace5489eeb6e15d7d49

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Message-Id: <20090412.181330.23529546.davem@davemloft.net>
Date:	Sun, 12 Apr 2009 18:13:30 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	paulmck@...ux.vnet.ibm.com
Cc:	paulus@...ba.org, mingo@...e.hu, torvalds@...ux-foundation.org,
	laijs@...fujitsu.com, shemminger@...tta.com,
	jeff.chua.linux@...il.com, dada1@...mosbay.com, jengelh@...ozas.de,
	kaber@...sh.net, r000n@...0n.net, linux-kernel@...r.kernel.org,
	netfilter-devel@...r.kernel.org, netdev@...r.kernel.org,
	benh@...nel.crashing.org
Subject: Re: iptables very slow after commit
 784544739a25c30637397ace5489eeb6e15d7d49

From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Date: Sun, 12 Apr 2009 10:31:08 -0700

> On Sun, Apr 12, 2009 at 09:34:27PM +1000, Paul Mackerras wrote:
>> Paul E. McKenney writes:
>> 
>> > If the generic implementation is needed only on !SMP systems, that
>> > could work.  The architectures I would be worried about include
>> > powerpc and ia64, which I believe support 32-bit SMP builds.
>> 
>> 32-bit powerpc doesn't have 64-bit atomic operations and does support
>> SMP.
>> 
>> What about ARM?  I thought they had 32-bit SMP these days as well.
> 
> Some of Steve Hemminger's recent suggestions in this thread seem to me
> to avoid this whole issue nicely.  But we will see!  ;-)

I hope so.

Eventually it seems that all of the older 32-bit SMP platforms
will be run under a bus having to execute some many "efficient"
primitives using the "hash table of spinlocks" scheme for
synchronization.
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