[Linuxarm] Re: [PATCH net-next] tcp: add tcp_tx_skb_cache_key checking in sk_stream_alloc_skb()

On 2021/9/1 18:39, Yunsheng Lin wrote:

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?

Hi, Eric Is there any implicit protection for sk->sk_tx_skb_cache? As my understanding, sk_stream_alloc_skb() seems to be protected by lock_sock(), and the sk_wmem_free_skb() seems to be mostly happening in NAPI polling for TCP(when ack packet is received) without lock_sock(), so it seems there is no protection here?