Re: [PATCH net-next-2.6] net: Increase NET_SKB_PAD to 64 bytes

Eric Dumazet
2010-05-07T05:15:29Z

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@davemloft.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