netdev - Re: [PATCH] ixgbe: fix truesize calculation when merging active tail into lro skb

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Message-ID: <1329241172.4818.4.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC>
Date:	Tue, 14 Feb 2012 18:39:32 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Alexander Duyck <alexander.h.duyck@...el.com>
Cc:	jeffrey.t.kirsher@...el.com, Christian Brunner <chb@....de>,
	netdev@...r.kernel.org,
	Jesse Brandeburg <jesse.brandeburg@...el.com>
Subject: Re: [PATCH] ixgbe: fix truesize calculation when merging active
 tail into lro skb

Le mardi 14 février 2012 à 09:21 -0800, Alexander Duyck a écrit :

> The code itself is correct, but the comment isn't.  This code path is
> applied only to the case where we are not using pages.  The default Rx
> buffer size is actually about 3K when RSC is in use, which means
> truesize is about 4.25K per buffer.
> 

Hmm... any reason its not 2.25K per buffer ? (assuming MTU=1500)

Do you really need this code in ixgbe_set_rx_buffer_len() ?

                /*
                 * Make best use of allocation by using all but 1K of a
                 * power of 2 allocation that will be used for skb->head.
                 */
                else if (max_frame <= IXGBE_RXBUFFER_3K)
                        rx_buf_len = IXGBE_RXBUFFER_3K;
                else if (max_frame <= IXGBE_RXBUFFER_7K)
                        rx_buf_len = IXGBE_RXBUFFER_7K;
                else if (max_frame <= IXGBE_RXBUFFER_15K)
                        rx_buf_len = IXGBE_RXBUFFER_15K;
                else
                        rx_buf_len = IXGBE_MAX_RXBUFFER;

Why not using :
		rx_buf_len = max_frame;

and let kmalloc() do its best ?



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