Since tcp_tx_skb_cache is disabled by default in: commit 0b7d7f6b2208 ("tcp: add tcp_tx_skb_cache sysctl") Add tcp_tx_skb_cache_key checking in sk_stream_alloc_skb() to avoid possible branch-misses. Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com> --- Also, the sk->sk_tx_skb_cache may be both changed by allocation and freeing side, I assume there may be some implicit protection here too, such as the NAPI protection for rx? --- net/ipv4/tcp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index e8b48df..226ddef 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -866,7 +866,7 @@ struct sk_buff *sk_stream_alloc_skb(struct sock *sk, int size, gfp_t gfp, { struct sk_buff *skb; - if (likely(!size)) { + if (static_branch_unlikely(&tcp_tx_skb_cache_key) && likely(!size)) { skb = sk->sk_tx_skb_cache; if (skb) { skb->truesize = SKB_TRUESIZE(skb_end_offset(skb)); -- 2.7.4