From a715dea3c8e9ef2771c534e05ee1d36f65987e64 Mon Sep 17 00:00:00 2001 From: Anton Blanchard Date: Sun, 27 Mar 2011 14:57:26 +0000 Subject: net: Always allocate at least 16 skb frags regardless of page size When analysing performance of the cxgb3 on a ppc64 box I noticed that we weren't doing much GRO merging. It turns out we are limited by the number of SKB frags: #define MAX_SKB_FRAGS (65536/PAGE_SIZE + 2) With a 4kB page size we have 18 frags, but with a 64kB page size we only have 3 frags. I ran a single stream TCP bandwidth test to compare the performance of Signed-off-by: David S. Miller --- include/linux/skbuff.h | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 24cfa626931..239083bfea1 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -122,8 +122,14 @@ struct sk_buff_head { struct sk_buff; -/* To allow 64K frame to be packed as single skb without frag_list */ +/* To allow 64K frame to be packed as single skb without frag_list. Since + * GRO uses frags we allocate at least 16 regardless of page size. + */ +#if (65536/PAGE_SIZE + 2) < 16 +#define MAX_SKB_FRAGS 16 +#else #define MAX_SKB_FRAGS (65536/PAGE_SIZE + 2) +#endif typedef struct skb_frag_struct skb_frag_t; -- cgit v1.2.3-70-g09d2