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Date: Thu, 22 Apr 2010 13:43:18 +0200 From: Eric Dumazet <eric.dumazet@...il.com> To: David Miller <davem@...emloft.net> Cc: netdev@...r.kernel.org Subject: Re: [PATCH] NIU support for skb->rxhash Le jeudi 22 avril 2010 à 04:21 -0700, David Miller a écrit : > But it turns out using it is largely pointless since the only way to > get the hash value(s) is through a structure which is prepended to the > packet data (so we take a cache miss on the packet data anyways) > instead of being able to fetch it out of the RX descriptors :-/ > > If anyone out there is trying to design sane hardware, please put the > following into your RX descriptors: > > 1) ethernet protocol type (u16) > 2) a flag bit indicating if the packet destination matched one > of the programmed unicast MAC addresses > 3) a flag bit indicating "multicast" > 4) a flag bit indicating "broadcast" > 5) at least 32-bits of the computed flow hash (u32) > > kthx, bye! Then, our stack also touch all 256 bytes of skb structure itself. offsetof(struct sk_buff, next) =0x0 offsetof(struct sk_buff, rxhash) =0xa8 offsetof(struct sk_buff, dev) =0x20 offsetof(struct sk_buff, len) =0x68 offsetof(struct sk_buff, protocol)=0x7e offsetof(struct sk_buff, network_header)=0xc0 offsetof(struct sk_buff, data) =0xd8 offsetof(struct sk_buff, head) =0xd0 Time for a reordering I guess ;) -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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