netdev - Re: [PATCH net-next-2.6] net: Increase NET_SKB

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Date:	Fri, 07 May 2010 11:55:14 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	monstr@...str.eu
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	hadi@...erus.ca, therbert@...gle.com,
	microblaze-uclinux@...e.uq.edu.au
Subject: Re: [PATCH net-next-2.6] net: Increase NET_SKB_PAD to 64 bytes

Le vendredi 07 mai 2010 à 11:48 +0200, Michal Simek a écrit :
> David Miller wrote:
> > From: Michal Simek <monstr@...str.eu>
> > Date: Fri, 07 May 2010 09:53:48 +0200
> > 
> >> I will add this Microblaze patch to my repo for testing and anyway
> >> should go through my repo.
> > 
> > It's already in the net-next-2.6 tree.
> 
> Anyway.
> 
> I am ok with removing NET_IP_ALIGN because it is already defined in 
> skbuff.h to 2.
> But increasing NET_SKB_PAD to 64 caused that Microblaze extends skb 
> buffers for some bytes.
> I measured it by iperf and netperf and I see regression around 1-2Mbit/s 
> that's why I would like to ask you to revert this patch or keep at least 
> NET_SKB_PAD part.

Interesting.

Increasing NET_SKB_PAD to say 128 or 256 should not have performance
impact, but reserve a bit more ram. (truesize...)

Investigation is needed. Maybe your NIC now allocates high order pages ?

What driver are you using ?


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