admin/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2025-12-07 20:06:24 +00:00
Code Issues Packages Projects Releases Wiki Activity

net: avoid extra access to sk->sk_wmem_alloc in sock_wfree()

Browse Source 
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>
This commit is contained in:
Eric Dumazet
2025-10-17 13:37:12 +00:00
committed by Paolo Abeni
parent d1d7998df9
commit 3ff9bcecce
2 changed files with 13 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

6
include/net/sock.h
View File

@@ -2607,12 +2607,16 @@ static inline struct page_frag *sk_page_frag(struct sock *sk)
bool sk_page_frag_refill(struct sock *sk, struct page_frag *pfrag);
static inline bool __sock_writeable(const struct sock *sk, int wmem_alloc)
{
return wmem_alloc < (READ_ONCE(sk->sk_sndbuf) >> 1);
}
/*
* Default write policy as shown to user space via poll/select/SIGIO
*/
static inline bool sock_writeable(const struct sock *sk)
{
return refcount_read(&sk->sk_wmem_alloc) < (READ_ONCE(sk->sk_sndbuf) >> 1);
return __sock_writeable(sk, refcount_read(&sk->sk_wmem_alloc));
}
static inline gfp_t gfp_any(void)

14
net/core/sock.c
View File

@@ -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() */