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net: add sk->sk_drop_counters

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Some sockets suffer from heavy false sharing on sk->sk_drops,
and fields in the same cache line.

Add sk->sk_drop_counters to:

- move the drop counter(s) to dedicated cache lines.
- Add basic NUMA awareness to these drop counter(s).

Following patches will use this infrastructure for UDP and RAW sockets.

sk_clone_lock() is not yet ready, it would need to properly
set newsk->sk_drop_counters if we plan to use this for TCP sockets.

v2: used Paolo suggestion from https://lore.kernel.org/netdev/8f09830a-d83d-43c9-b36b-88ba0a23e9b2@redhat.com/

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250826125031.1578842-4-edumazet@google.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Eric Dumazet 2025-08-26 12:50:29 +00:00 committed by Paolo Abeni
parent cb4d5a6eb6
commit c51613fa27
2 changed files with 33 additions and 1 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

32
include/net/sock.h
View file

@ -102,6 +102,11 @@ struct net;
typedef __u32 __bitwise __portpair;
typedef __u64 __bitwise __addrpair;
struct socket_drop_counters {
atomic_t drops0 ____cacheline_aligned_in_smp;
atomic_t drops1 ____cacheline_aligned_in_smp;
};
/**
* struct sock_common - minimal network layer representation of sockets
* @skc_daddr: Foreign IPv4 addr
@ -282,6 +287,7 @@ struct sk_filter;
* @sk_err_soft: errors that don't cause failure but are the cause of a
* persistent failure not just 'timed out'
* @sk_drops: raw/udp drops counter
* @sk_drop_counters: optional pointer to socket_drop_counters
* @sk_ack_backlog: current listen backlog
* @sk_max_ack_backlog: listen backlog set in listen()
* @sk_uid: user id of owner
@ -449,6 +455,7 @@ struct sock {
#ifdef CONFIG_XFRM
struct xfrm_policy __rcu *sk_policy[2];
#endif
struct socket_drop_counters *sk_drop_counters;
__cacheline_group_end(sock_read_rxtx);
__cacheline_group_begin(sock_write_rxtx);
@ -2684,7 +2691,18 @@ struct sock_skb_cb {
static inline void sk_drops_add(struct sock *sk, int segs)
{
atomic_add(segs, &sk->sk_drops);
struct socket_drop_counters *sdc = sk->sk_drop_counters;
if (sdc) {
int n = numa_node_id() % 2;
if (n)
atomic_add(segs, &sdc->drops1);
else
atomic_add(segs, &sdc->drops0);
} else {
atomic_add(segs, &sk->sk_drops);
}
}
static inline void sk_drops_inc(struct sock *sk)
@ -2694,11 +2712,23 @@ static inline void sk_drops_inc(struct sock *sk)
static inline int sk_drops_read(const struct sock *sk)
{
const struct socket_drop_counters *sdc = sk->sk_drop_counters;
if (sdc) {
DEBUG_NET_WARN_ON_ONCE(atomic_read(&sk->sk_drops));
return atomic_read(&sdc->drops0) + atomic_read(&sdc->drops1);
}
return atomic_read(&sk->sk_drops);
}
static inline void sk_drops_reset(struct sock *sk)
{
struct socket_drop_counters *sdc = sk->sk_drop_counters;
if (sdc) {
atomic_set(&sdc->drops0, 0);
atomic_set(&sdc->drops1, 0);
}
atomic_set(&sk->sk_drops, 0);
}

2
net/core/sock.c
View file

@ -2505,6 +2505,7 @@ struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority)
newsk->sk_wmem_queued = 0;
newsk->sk_forward_alloc = 0;
newsk->sk_reserved_mem = 0;
DEBUG_NET_WARN_ON_ONCE(newsk->sk_drop_counters);
sk_drops_reset(newsk);
newsk->sk_send_head = NULL;
newsk->sk_userlocks = sk->sk_userlocks & ~SOCK_BINDPORT_LOCK;
@ -4457,6 +4458,7 @@ static int __init sock_struct_check(void)
#ifdef CONFIG_MEMCG
CACHELINE_ASSERT_GROUP_MEMBER(struct sock, sock_read_rxtx, sk_memcg);
#endif
CACHELINE_ASSERT_GROUP_MEMBER(struct sock, sock_read_rxtx, sk_drop_counters);
CACHELINE_ASSERT_GROUP_MEMBER(struct sock, sock_write_rxtx, sk_lock);
CACHELINE_ASSERT_GROUP_MEMBER(struct sock, sock_write_rxtx, sk_reserved_mem);