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Date: Sun, 13 Nov 2011 22:08:15 +0200 From: "Eilon Greenstein" <eilong@...adcom.com> To: "Eric Dumazet" <eric.dumazet@...il.com> cc: "David Miller" <davem@...emloft.net>, "bhutchings@...arflare.com" <bhutchings@...arflare.com>, "pstaszewski@...are.pl" <pstaszewski@...are.pl>, "netdev@...r.kernel.org" <netdev@...r.kernel.org> Subject: Re: [PATCH net-next] bnx2x: reduce skb truesize by 50% On Sun, 2011-11-13 at 11:42 -0800, Eric Dumazet wrote: > Le dimanche 13 novembre 2011 à 20:53 +0200, Eilon Greenstein a écrit : > > > I’m not sure I’m following the math over here. Assuming L1 is 64 bytes, > > we need up to 63 bytes to align the start address (assuming SLOB is > > being used) and additional (up to) 63 bytes at the end. That can sum up > > to 126 bytes am I missing something? > > > > What do you really mean by aligning the end ? I mean padding it to full cache line. > How can both start and end of a frame can be aligned ? The packet will start at aligned address and (using padding) will end at cache line boundaries. > If hardware needs extra room after the end of frame, then we already > have it (since we store struct skb_shared_info here) We have some space in there, but as far as I can tell it's not up to 63 bytes, right? We will overrun the dataref. Thanks, Eilon -- 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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