Commit d9a58a78 authored by Ian Campbell's avatar Ian Campbell Committed by David S. Miller
Browse files

xen/netfront: improve truesize tracking 



Using RX_COPY_THRESHOLD is incorrect if the SKB is actually smaller
than that. We have already accounted for this in
NETFRONT_SKB_CB(skb)->pull_to so use that instead.

Fixes WARN_ON from skb_try_coalesce.

Signed-off-by: default avatarIan Campbell <ian.campbell@citrix.com>
Cc: Sander Eikelenboom <linux@eikelenboom.it>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: annie li <annie.li@oracle.com>
Cc: xen-devel@lists.xen.org
Cc: netdev@vger.kernel.org
Cc: stable@kernel.org # 3.7.x only
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 32fa10b2

drivers/net/xen-netfront.c

+4 −23
Original line number Diff line number Diff line
@@ -1015,29 +1015,10 @@ err: 
		i = xennet_fill_frags(np, skb, &tmpq);



		/*

		 * Truesize approximates the size of true data plus

		 * any supervisor overheads. Adding hypervisor

		 * overheads has been shown to significantly reduce

		 * achievable bandwidth with the default receive

		 * buffer size. It is therefore not wise to account

		 * for it here.

		 *

		 * After alloc_skb(RX_COPY_THRESHOLD), truesize is set

		 * to RX_COPY_THRESHOLD + the supervisor

		 * overheads. Here, we add the size of the data pulled

		 * in xennet_fill_frags().

		 *

		 * We also adjust for any unused space in the main

		 * data area by subtracting (RX_COPY_THRESHOLD -

		 * len). This is especially important with drivers

		 * which split incoming packets into header and data,

		 * using only 66 bytes of the main data area (see the

		 * e1000 driver for example.)  On such systems,

		 * without this last adjustement, our achievable

		 * receive throughout using the standard receive

		 * buffer size was cut by 25%(!!!).

                 * Truesize is the actual allocation size, even if the

                 * allocation is only partially used.

                 */

		skb->truesize += skb->data_len - RX_COPY_THRESHOLD;

		skb->truesize += PAGE_SIZE * skb_shinfo(skb)->nr_frags;

		skb->len += skb->data_len;



		if (rx->flags & XEN_NETRXF_csum_blank)

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