From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roland Dreier Subject: Re: [PATCHv10 08/12] mlx4: Add support for IBoE - address resolution Date: Thu, 21 Oct 2010 21:15:35 -0700 Message-ID: References: <20100826141851.GI8795@mtldesk30> <20101021230307.GD6367@mtldesk30> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: In-Reply-To: <20101021230307.GD6367@mtldesk30> (Eli Cohen's message of "Fri, 22 Oct 2010 01:03:07 +0200") Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Eli Cohen Cc: RDMA list List-Id: linux-rdma@vger.kernel.org > I don't get this. For IB, we have 72 without immediate - did you > forget to add the ICRC? I think we count it with the header... We don't need ICRC in the header_buf, do we? We're talking about MLX4_IB_UD_HEADER_SIZE, which is used to hold the packet header we get from ib_ud_header_pack(). The ICRC is accounted for in a different segment of the WQE. In any case, it shouldn't matter -- I don't see how it could be correct to increase the buffer size by 4 bytes to account for the change from LRH to Ethernet header; an LRH is 8 bytes and an Ethernet header (without .1q etc) is 14 bytes. So we should add 6 bytes, right? The math I get is IB: LRH + GRH + BTH + DETH + IMM 8 40 12 8 4 = 72 Eth: MAC + GRH + BTH + DETH + IMM 14 40 12 8 4 = 78 I don't see how your change > - MLX4_IB_UD_HEADER_SIZE = 72, > + MLX4_IB_UD_HEADER_SIZE = 76, could possibly be correct, although as I said it probably works because of padding and not hitting the worst case in practice anyway. - R. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html