diff options
| author | Eric Dumazet <edumazet@google.com> | 2025-10-17 13:37:12 +0000 |
|---|---|---|
| committer | Paolo Abeni <pabeni@redhat.com> | 2025-10-21 15:56:21 +0200 |
| commit | 3ff9bcecce83f12169ab3e42671bd76554ca521a (patch) | |
| tree | db362844461ecef320cd31a69cd3121b533c8618 /net/core | |
| parent | d1d7998df9d7d3ee20bcfc876065fa897b11506d (diff) | |
net: avoid extra access to sk->sk_wmem_alloc in sock_wfree()
UDP TX packets destructor is sock_wfree().
It suffers from a cache line bouncing in sock_def_write_space_wfree().
Instead of reading sk->sk_wmem_alloc after we just did an atomic RMW
on it, use __refcount_sub_and_test() to get the old value for free,
and pass the new value to sock_def_write_space_wfree().
Add __sock_writeable() helper.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20251017133712.2842665-1-edumazet@google.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Diffstat (limited to 'net/core')
| -rw-r--r-- | net/core/sock.c | 14 |
1 files changed, 8 insertions, 6 deletions
diff --git a/net/core/sock.c b/net/core/sock.c index b78533fb9268..a99132cc0965 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -155,7 +155,7 @@ static DEFINE_MUTEX(proto_list_mutex); static LIST_HEAD(proto_list); -static void sock_def_write_space_wfree(struct sock *sk); +static void sock_def_write_space_wfree(struct sock *sk, int wmem_alloc); static void sock_def_write_space(struct sock *sk); /** @@ -2659,16 +2659,18 @@ EXPORT_SYMBOL_GPL(sk_setup_caps); */ void sock_wfree(struct sk_buff *skb) { - struct sock *sk = skb->sk; unsigned int len = skb->truesize; + struct sock *sk = skb->sk; bool free; + int old; if (!sock_flag(sk, SOCK_USE_WRITE_QUEUE)) { if (sock_flag(sk, SOCK_RCU_FREE) && sk->sk_write_space == sock_def_write_space) { rcu_read_lock(); - free = refcount_sub_and_test(len, &sk->sk_wmem_alloc); - sock_def_write_space_wfree(sk); + free = __refcount_sub_and_test(len, &sk->sk_wmem_alloc, + &old); + sock_def_write_space_wfree(sk, old - len); rcu_read_unlock(); if (unlikely(free)) __sk_free(sk); @@ -3612,12 +3614,12 @@ static void sock_def_write_space(struct sock *sk) * for SOCK_RCU_FREE sockets under RCU read section and after putting * ->sk_wmem_alloc. */ -static void sock_def_write_space_wfree(struct sock *sk) +static void sock_def_write_space_wfree(struct sock *sk, int wmem_alloc) { /* Do not wake up a writer until he can make "significant" * progress. --DaveM */ - if (sock_writeable(sk)) { + if (__sock_writeable(sk, wmem_alloc)) { struct socket_wq *wq = rcu_dereference(sk->sk_wq); /* rely on refcount_sub from sock_wfree() */ |