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authorAnton Blanchard <anton@samba.org>2011-03-27 14:57:26 +0000
committerDavid S. Miller <davem@davemloft.net>2011-03-28 22:26:32 -0700
commita715dea3c8e9ef2771c534e05ee1d36f65987e64 (patch)
tree7734586473abed25f7ec4b8423adbdba3d829a61 /include/linux/skbuff.h
parent4910ac6c526d2868adcb5893e0c428473de862b5 (diff)
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 <davem@davemloft.net>
Diffstat (limited to 'include/linux/skbuff.h')
-rw-r--r--include/linux/skbuff.h8
1 files changed, 7 insertions, 1 deletions
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;