| Message ID | 20210314111027.7657-7-alobakin@pm.me |
|---|---|
| State | New |
| Headers | show |
| Series | skbuff: micro-optimize flow dissection | expand |
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 46c61e127e9f..ecc029674ae4 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -3680,11 +3680,10 @@ static inline void * __must_check __skb_header_pointer(const struct sk_buff *skb, int offset, int len, const void *data, int hlen, void *buffer) { - if (hlen - offset >= len) + if (likely(hlen - offset >= len)) return (void *)data + offset; - if (!skb || - skb_copy_bits(skb, offset, buffer, len) < 0) + if (!skb || unlikely(skb_copy_bits(skb, offset, buffer, len) < 0)) return NULL; return buffer;
{,__}skb_header_pointer() helpers exist mainly for preventing accesses-beyond-end of the linear data. In the vast majorify of cases, they bail out on the first condition. All code going after is mostly a fallback. Mark the most common branch as 'likely' one to move it in-line. Also, skb_copy_bits() can return negative values only when the input arguments are invalid, e.g. offset is greater than skb->len. It can be safely marked as 'unlikely' branch, assuming that hotpath code provides sane input to not fail here. These two bump the throughput with a single Flow Dissector pass on every packet (e.g. with RPS or driver that uses eth_get_headlen()) on 20 Mbps per flow/core. Signed-off-by: Alexander Lobakin <alobakin@pm.me> --- include/linux/skbuff.h | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) -- 2.30.2