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authorEric Dumazet <eric.dumazet@gmail.com>2011-10-13 07:28:54 +0000
committerDavid S. Miller <davem@davemloft.net>2011-10-13 16:05:07 -0400
commit87fb4b7b533073eeeaed0b6bf7c2328995f6c075 (patch)
treebe4b37f08d7fe2d018ae68bae4577b1b2bafd0fc /include/linux/skbuff.h
parent97ba0eb64ca690165f945a83e609102fcefa99cb (diff)
net: more accurate skb truesize
skb truesize currently accounts for sk_buff struct and part of skb head. kmalloc() roundings are also ignored. Considering that skb_shared_info is larger than sk_buff, its time to take it into account for better memory accounting. This patch introduces SKB_TRUESIZE(X) macro to centralize various assumptions into a single place. At skb alloc phase, we put skb_shared_info struct at the exact end of skb head, to allow a better use of memory (lowering number of reallocations), since kmalloc() gives us power-of-two memory blocks. Unless SLUB/SLUB debug is active, both skb->head and skb_shared_info are aligned to cache lines, as before. Note: This patch might trigger performance regressions because of misconfigured protocol stacks, hitting per socket or global memory limits that were previously not reached. But its a necessary step for a more accurate memory accounting. Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> CC: Andi Kleen <ak@linux.intel.com> CC: Ben Hutchings <bhutchings@solarflare.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/linux/skbuff.h')
-rw-r--r--include/linux/skbuff.h5
1 files changed, 5 insertions, 0 deletions
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index ac6b05a325c..64f86951ef7 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -46,6 +46,11 @@
#define SKB_MAX_HEAD(X) (SKB_MAX_ORDER((X), 0))
#define SKB_MAX_ALLOC (SKB_MAX_ORDER(0, 2))
+/* return minimum truesize of one skb containing X bytes of data */
+#define SKB_TRUESIZE(X) ((X) + \
+ SKB_DATA_ALIGN(sizeof(struct sk_buff)) + \
+ SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))
+
/* A. Checksumming of received packets by device.
*
* NONE: device failed to checksum this packet.