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

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Date:	Fri, 07 May 2010 07:15:21 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org, hadi@...erus.ca, therbert@...gle.com,
	monstr@...str.eu, microblaze-uclinux@...e.uq.edu.au
Subject: Re: [PATCH net-next-2.6] net: Increase NET_SKB_PAD to 64 bytes

Le jeudi 06 mai 2010 à 22:02 -0700, David Miller a écrit :

> Seeing this made me go check who was overriding NET_IP_ALIGN or
> NET_SKB_PAD.
> 
> The powerpc bits are legitimate, but the microblaze case is complete
> bogosity.  It defines NET_IP_ALIGN to the default (2) and sets
> NET_SKB_PAD to L1_CACHE_BYTES which on microblaze is 4 and
> significantly smaller than the default.
> 
> So I'm going to delete them in net-next-2.6 like so:
> 
> --------------------
> microblaze: Kill NET_SKB_PAD and NET_IP_ALIGN overrides.
> 
> NET_IP_ALIGN defaults to 2, no need to override.
> 
> NET_SKB_PAD is now 64, which is much larger than microblaze's
> L1_CACHE_SIZE so no need to override that either.
> 
> Signed-off-by: David S. Miller <davem@...emloft.net>
> ---
>  arch/microblaze/include/asm/system.h |   10 ----------
>  1 files changed, 0 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/microblaze/include/asm/system.h b/arch/microblaze/include/asm/system.h
> index 48c4f03..b1e2f07 100644
> --- a/arch/microblaze/include/asm/system.h
> +++ b/arch/microblaze/include/asm/system.h
> @@ -97,14 +97,4 @@ extern struct dentry *of_debugfs_root;
>  
>  #define arch_align_stack(x) (x)
>  
> -/*
> - * MicroBlaze doesn't handle unaligned accesses in hardware.
> - *
> - * Based on this we force the IP header alignment in network drivers.
> - * We also modify NET_SKB_PAD to be a cacheline in size, thus maintaining
> - * cacheline alignment of buffers.
> - */
> -#define NET_IP_ALIGN	2
> -#define NET_SKB_PAD	L1_CACHE_BYTES
> -
>  #endif /* _ASM_MICROBLAZE_SYSTEM_H */

Yes, this seems strange it actually worked if L1_CACHE_BYTES = 4

Thanks


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