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Message-ID: <CAAVpQUCiSJnv9QMuAFbomEeF3D=0iJYSJSmMhpQpyCFxQUgK_A@mail.gmail.com>
Date: Mon, 25 Aug 2025 13:19:14 -0700
From: Kuniyuki Iwashima <kuniyu@...gle.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, netdev@...r.kernel.org,
eric.dumazet@...il.com, Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH net-next 3/3] net: add new sk->sk_drops1 field
On Mon, Aug 25, 2025 at 12:59 PM Eric Dumazet <edumazet@...gle.com> wrote:
>
> sk->sk_drops can be heavily contended when
> changed from many cpus.
>
> Instead using too expensive per-cpu data structure,
> add a second sk->sk_drops1 field and change
> sk_drops_inc() to be NUMA aware.
>
> This patch adds 64 bytes per socket.
>
> For hosts having more than two memory nodes, sk_drops_inc()
> might not be optimal and can be refined later.
>
> Tested with the following stress test, sending about 11 Mpps
> to a dual socket AMD EPYC 7B13 64-Core.
>
> super_netperf 20 -t UDP_STREAM -H DUT -l10 -- -n -P,1000 -m 120
> Note: due to socket lookup, only one UDP socket will receive
> packets on DUT.
>
> Then measure receiver (DUT) behavior. We can see
> consumer and BH handlers can process more packets per second.
>
> Before:
>
> nstat -n ; sleep 1 ; nstat | grep Udp
> Udp6InDatagrams 855592 0.0
> Udp6InErrors 5621467 0.0
> Udp6RcvbufErrors 5621467 0.0
>
> After:
> nstat -n ; sleep 1 ; nstat | grep Udp
> Udp6InDatagrams 914537 0.0
> Udp6InErrors 6888487 0.0
> Udp6RcvbufErrors 6888487 0.0
>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> ---
> include/net/sock.h | 20 +++++++++++++++++++
> .../selftests/bpf/progs/bpf_iter_netlink.c | 3 ++-
> .../selftests/bpf/progs/bpf_iter_udp4.c | 2 +-
> .../selftests/bpf/progs/bpf_iter_udp6.c | 2 +-
> 4 files changed, 24 insertions(+), 3 deletions(-)
>
> diff --git a/include/net/sock.h b/include/net/sock.h
> index f40e3c4883be32c8282694ab215bcf79eb87cbd7..318169eb1a3d40eefac50147012551614abc6f7a 100644
> --- a/include/net/sock.h
> +++ b/include/net/sock.h
> @@ -282,6 +282,7 @@ 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_drops1: second drops counter
> * @sk_ack_backlog: current listen backlog
> * @sk_max_ack_backlog: listen backlog set in listen()
> * @sk_uid: user id of owner
> @@ -571,6 +572,11 @@ struct sock {
> atomic_t sk_drops ____cacheline_aligned_in_smp;
> struct rcu_head sk_rcu;
> netns_tracker ns_tracker;
> +#if defined(CONFIG_NUMA)
> + atomic_t sk_drops1 ____cacheline_aligned_in_smp;
> +#else
> + atomic_t sk_drops1;
Is this #else to be friendly to bpf selftests ?
> +#endif
> };
>
> struct sock_bh_locked {
> @@ -2684,17 +2690,31 @@ struct sock_skb_cb {
>
> static inline void sk_drops_inc(struct sock *sk)
> {
> +#if defined(CONFIG_NUMA)
> + int n = numa_node_id() % 2;
> +
> + if (n)
> + atomic_inc(&sk->sk_drops1);
> + else
> + atomic_inc(&sk->sk_drops);
> +#else
> atomic_inc(&sk->sk_drops);
> +#endif
> }
>
> static inline int sk_drops_read(const struct sock *sk)
> {
> +#if defined(CONFIG_NUMA)
> + return atomic_read(&sk->sk_drops) + atomic_read(&sk->sk_drops1);
> +#else
> return atomic_read(&sk->sk_drops);
> +#endif
> }
>
> static inline void sk_drops_reset(struct sock *sk)
> {
> atomic_set(&sk->sk_drops, 0);
> + atomic_set(&sk->sk_drops1, 0);
> }
>
> static inline void
> diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_netlink.c b/tools/testing/selftests/bpf/progs/bpf_iter_netlink.c
> index 00b2ceae81fb0914f2de3634eb342004e8bc3c5b..31ad9fcc6022d5d31b9c6a35daacaad7c887a51f 100644
> --- a/tools/testing/selftests/bpf/progs/bpf_iter_netlink.c
> +++ b/tools/testing/selftests/bpf/progs/bpf_iter_netlink.c
> @@ -57,7 +57,8 @@ int dump_netlink(struct bpf_iter__netlink *ctx)
> inode = SOCK_INODE(sk);
> bpf_probe_read_kernel(&ino, sizeof(ino), &inode->i_ino);
> }
> - BPF_SEQ_PRINTF(seq, "%-8u %-8lu\n", s->sk_drops.counter, ino);
> + BPF_SEQ_PRINTF(seq, "%-8u %-8lu\n",
> + s->sk_drops.counter + s->sk_drops1.counter, ino);
>
> return 0;
> }
> diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_udp4.c b/tools/testing/selftests/bpf/progs/bpf_iter_udp4.c
> index ffbd4b116d17ffbb9f14440c788e50490fb0f4e0..192ab5693a7131c1ec5879e539651c21f6f3c9ae 100644
> --- a/tools/testing/selftests/bpf/progs/bpf_iter_udp4.c
> +++ b/tools/testing/selftests/bpf/progs/bpf_iter_udp4.c
> @@ -64,7 +64,7 @@ int dump_udp4(struct bpf_iter__udp *ctx)
> 0, 0L, 0, ctx->uid, 0,
> sock_i_ino(&inet->sk),
> inet->sk.sk_refcnt.refs.counter, udp_sk,
> - inet->sk.sk_drops.counter);
> + inet->sk.sk_drops.counter + inet->sk.sk_drops1.counter);
>
> return 0;
> }
> diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_udp6.c b/tools/testing/selftests/bpf/progs/bpf_iter_udp6.c
> index 47ff7754f4fda4c9db92fbf1dc2e6a68f044174e..5170bdf458fa1b9a4eea9240fbaa5934182a7776 100644
> --- a/tools/testing/selftests/bpf/progs/bpf_iter_udp6.c
> +++ b/tools/testing/selftests/bpf/progs/bpf_iter_udp6.c
> @@ -72,7 +72,7 @@ int dump_udp6(struct bpf_iter__udp *ctx)
> 0, 0L, 0, ctx->uid, 0,
> sock_i_ino(&inet->sk),
> inet->sk.sk_refcnt.refs.counter, udp_sk,
> - inet->sk.sk_drops.counter);
> + inet->sk.sk_drops.counter + inet->sk.sk_drops1.counter);
>
> return 0;
> }
> --
> 2.51.0.261.g7ce5a0a67e-goog
>
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