From 87fb4b7b533073eeeaed0b6bf7c2328995f6c075 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 13 Oct 2011 07:28:54 +0000 Subject: 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 CC: Andi Kleen CC: Ben Hutchings Signed-off-by: David S. Miller --- include/linux/skbuff.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'include/linux') diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index ac6b05a325cc..64f86951ef74 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. -- cgit v1.2.3