netdev - Re: [PATCH 3/3] Convert the UDP hash lock to RCU

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Date:	Tue, 7 Oct 2008 18:29:02 +0400
From:	Evgeniy Polyakov <johnpol@....mipt.ru>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	Corey Minyard <minyard@....org>,
	David Miller <davem@...emloft.net>, dada1@...mosbay.com,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	shemminger@...tta.com, paulmck@...ux.vnet.ibm.com
Subject: Re: [PATCH 3/3] Convert the UDP hash lock to RCU

On Tue, Oct 07, 2008 at 09:16:13AM -0500, Christoph Lameter (cl@...ux-foundation.org) wrote:
> > I tested skb destruction via RCU path, and got 2.5 times worse numbers
> > with small-packets-bulk-transfer workload.
> 
> Was this with regular RCU freeing? This will cool down the cacheline before
> frees. You need SLAB_DESTROY_BY_RCU to keep the objects cache hot.

I believe there were no SLAB_DESTROY_BY_RCU 2 yars ago :)

It was pure call_rcu(&skb->rcu, real_skb_freeing), where
real_skb_freeing() just did usual kfree().

-- 
	Evgeniy Polyakov
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