Re: [PATCH v2 net-next 2/2] net: introduce SO_INCOMING_CPU

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[CC += linux-api@]

On Tue, Nov 11, 2014 at 2:54 PM, Eric Dumazet <edumazet@xxxxxxxxxx> wrote:
> Alternative to RPS/RFS is to use hardware support for multiple
> queues.
>
> Then split a set of million of sockets into worker threads, each
> one using epoll() to manage events on its own socket pool.
>
> Ideally, we want one thread per RX/TX queue/cpu, but we have no way to
> know after accept() or connect() on which queue/cpu a socket is managed.
>
> We normally use one cpu per RX queue (IRQ smp_affinity being properly
> set), so remembering on socket structure which cpu delivered last packet
> is enough to solve the problem.
>
> After accept(), connect(), or even file descriptor passing around
> processes, applications can use :
>
>  int cpu;
>  socklen_t len = sizeof(cpu);
>
>  getsockopt(fd, SOL_SOCKET, SO_INCOMING_CPU, &cpu, &len);
>
> And use this information to put the socket into the right silo
> for optimal performance, as all networking stack should run
> on the appropriate cpu, without need to send IPI (RPS/RFS).
>
> Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
> ---
>  arch/alpha/include/uapi/asm/socket.h   |  2 ++
>  arch/avr32/include/uapi/asm/socket.h   |  2 ++
>  arch/cris/include/uapi/asm/socket.h    |  2 ++
>  arch/frv/include/uapi/asm/socket.h     |  2 ++
>  arch/ia64/include/uapi/asm/socket.h    |  2 ++
>  arch/m32r/include/uapi/asm/socket.h    |  2 ++
>  arch/mips/include/uapi/asm/socket.h    |  2 ++
>  arch/mn10300/include/uapi/asm/socket.h |  2 ++
>  arch/parisc/include/uapi/asm/socket.h  |  2 ++
>  arch/powerpc/include/uapi/asm/socket.h |  2 ++
>  arch/s390/include/uapi/asm/socket.h    |  2 ++
>  arch/sparc/include/uapi/asm/socket.h   |  2 ++
>  arch/xtensa/include/uapi/asm/socket.h  |  2 ++
>  include/net/sock.h                     | 12 ++++++++++++
>  include/uapi/asm-generic/socket.h      |  2 ++
>  net/core/sock.c                        |  5 +++++
>  net/ipv4/tcp_ipv4.c                    |  1 +
>  net/ipv4/udp.c                         |  1 +
>  net/ipv6/tcp_ipv6.c                    |  1 +
>  net/ipv6/udp.c                         |  1 +
>  net/sctp/ulpqueue.c                    |  5 +++--
>  21 files changed, 52 insertions(+), 2 deletions(-)
>
> diff --git a/arch/alpha/include/uapi/asm/socket.h b/arch/alpha/include/uapi/asm/socket.h
> index 3de1394bcab8..e2fe0700b3b4 100644
> --- a/arch/alpha/include/uapi/asm/socket.h
> +++ b/arch/alpha/include/uapi/asm/socket.h
> @@ -87,4 +87,6 @@
>
>  #define SO_BPF_EXTENSIONS      48
>
> +#define SO_INCOMING_CPU                49
> +
>  #endif /* _UAPI_ASM_SOCKET_H */
> diff --git a/arch/avr32/include/uapi/asm/socket.h b/arch/avr32/include/uapi/asm/socket.h
> index 6e6cd159924b..92121b0f5b98 100644
> --- a/arch/avr32/include/uapi/asm/socket.h
> +++ b/arch/avr32/include/uapi/asm/socket.h
> @@ -80,4 +80,6 @@
>
>  #define SO_BPF_EXTENSIONS      48
>
> +#define SO_INCOMING_CPU                49
> +
>  #endif /* _UAPI__ASM_AVR32_SOCKET_H */
> diff --git a/arch/cris/include/uapi/asm/socket.h b/arch/cris/include/uapi/asm/socket.h
> index ed94e5ed0a23..60f60f5b9b35 100644
> --- a/arch/cris/include/uapi/asm/socket.h
> +++ b/arch/cris/include/uapi/asm/socket.h
> @@ -82,6 +82,8 @@
>
>  #define SO_BPF_EXTENSIONS      48
>
> +#define SO_INCOMING_CPU                49
> +
>  #endif /* _ASM_SOCKET_H */
>
>
> diff --git a/arch/frv/include/uapi/asm/socket.h b/arch/frv/include/uapi/asm/socket.h
> index ca2c6e6f31c6..2c6890209ea6 100644
> --- a/arch/frv/include/uapi/asm/socket.h
> +++ b/arch/frv/include/uapi/asm/socket.h
> @@ -80,5 +80,7 @@
>
>  #define SO_BPF_EXTENSIONS      48
>
> +#define SO_INCOMING_CPU                49
> +
>  #endif /* _ASM_SOCKET_H */
>
> diff --git a/arch/ia64/include/uapi/asm/socket.h b/arch/ia64/include/uapi/asm/socket.h
> index a1b49bac7951..09a93fb566f6 100644
> --- a/arch/ia64/include/uapi/asm/socket.h
> +++ b/arch/ia64/include/uapi/asm/socket.h
> @@ -89,4 +89,6 @@
>
>  #define SO_BPF_EXTENSIONS      48
>
> +#define SO_INCOMING_CPU                49
> +
>  #endif /* _ASM_IA64_SOCKET_H */
> diff --git a/arch/m32r/include/uapi/asm/socket.h b/arch/m32r/include/uapi/asm/socket.h
> index 6c9a24b3aefa..e8589819c274 100644
> --- a/arch/m32r/include/uapi/asm/socket.h
> +++ b/arch/m32r/include/uapi/asm/socket.h
> @@ -80,4 +80,6 @@
>
>  #define SO_BPF_EXTENSIONS      48
>
> +#define SO_INCOMING_CPU                49
> +
>  #endif /* _ASM_M32R_SOCKET_H */
> diff --git a/arch/mips/include/uapi/asm/socket.h b/arch/mips/include/uapi/asm/socket.h
> index a14baa218c76..2e9ee8c55a10 100644
> --- a/arch/mips/include/uapi/asm/socket.h
> +++ b/arch/mips/include/uapi/asm/socket.h
> @@ -98,4 +98,6 @@
>
>  #define SO_BPF_EXTENSIONS      48
>
> +#define SO_INCOMING_CPU                49
> +
>  #endif /* _UAPI_ASM_SOCKET_H */
> diff --git a/arch/mn10300/include/uapi/asm/socket.h b/arch/mn10300/include/uapi/asm/socket.h
> index 6aa3ce1854aa..f3492e8c9f70 100644
> --- a/arch/mn10300/include/uapi/asm/socket.h
> +++ b/arch/mn10300/include/uapi/asm/socket.h
> @@ -80,4 +80,6 @@
>
>  #define SO_BPF_EXTENSIONS      48
>
> +#define SO_INCOMING_CPU                49
> +
>  #endif /* _ASM_SOCKET_H */
> diff --git a/arch/parisc/include/uapi/asm/socket.h b/arch/parisc/include/uapi/asm/socket.h
> index fe35ceacf0e7..7984a1cab3da 100644
> --- a/arch/parisc/include/uapi/asm/socket.h
> +++ b/arch/parisc/include/uapi/asm/socket.h
> @@ -79,4 +79,6 @@
>
>  #define SO_BPF_EXTENSIONS      0x4029
>
> +#define SO_INCOMING_CPU                0x402A
> +
>  #endif /* _UAPI_ASM_SOCKET_H */
> diff --git a/arch/powerpc/include/uapi/asm/socket.h b/arch/powerpc/include/uapi/asm/socket.h
> index a9c3e2e18c05..3474e4ef166d 100644
> --- a/arch/powerpc/include/uapi/asm/socket.h
> +++ b/arch/powerpc/include/uapi/asm/socket.h
> @@ -87,4 +87,6 @@
>
>  #define SO_BPF_EXTENSIONS      48
>
> +#define SO_INCOMING_CPU                49
> +
>  #endif /* _ASM_POWERPC_SOCKET_H */
> diff --git a/arch/s390/include/uapi/asm/socket.h b/arch/s390/include/uapi/asm/socket.h
> index e031332096d7..8457636c33e1 100644
> --- a/arch/s390/include/uapi/asm/socket.h
> +++ b/arch/s390/include/uapi/asm/socket.h
> @@ -86,4 +86,6 @@
>
>  #define SO_BPF_EXTENSIONS      48
>
> +#define SO_INCOMING_CPU                49
> +
>  #endif /* _ASM_SOCKET_H */
> diff --git a/arch/sparc/include/uapi/asm/socket.h b/arch/sparc/include/uapi/asm/socket.h
> index 54d9608681b6..4a8003a94163 100644
> --- a/arch/sparc/include/uapi/asm/socket.h
> +++ b/arch/sparc/include/uapi/asm/socket.h
> @@ -76,6 +76,8 @@
>
>  #define SO_BPF_EXTENSIONS      0x0032
>
> +#define SO_INCOMING_CPU                0x0033
> +
>  /* Security levels - as per NRL IPv6 - don't actually do anything */
>  #define SO_SECURITY_AUTHENTICATION             0x5001
>  #define SO_SECURITY_ENCRYPTION_TRANSPORT       0x5002
> diff --git a/arch/xtensa/include/uapi/asm/socket.h b/arch/xtensa/include/uapi/asm/socket.h
> index 39acec0cf0b1..c46f6a696849 100644
> --- a/arch/xtensa/include/uapi/asm/socket.h
> +++ b/arch/xtensa/include/uapi/asm/socket.h
> @@ -91,4 +91,6 @@
>
>  #define SO_BPF_EXTENSIONS      48
>
> +#define SO_INCOMING_CPU                49
> +
>  #endif /* _XTENSA_SOCKET_H */
> diff --git a/include/net/sock.h b/include/net/sock.h
> index 7db3db112baa..ff2c3f11fb8f 100644
> --- a/include/net/sock.h
> +++ b/include/net/sock.h
> @@ -273,6 +273,7 @@ struct cg_proto;
>    *    @sk_rcvtimeo: %SO_RCVTIMEO setting
>    *    @sk_sndtimeo: %SO_SNDTIMEO setting
>    *    @sk_rxhash: flow hash received from netif layer
> +  *    @sk_incoming_cpu: record cpu processing incoming packets
>    *    @sk_txhash: computed flow hash for use on transmit
>    *    @sk_filter: socket filtering instructions
>    *    @sk_protinfo: private area, net family specific, when not using slab
> @@ -350,6 +351,12 @@ struct sock {
>  #ifdef CONFIG_RPS
>         __u32                   sk_rxhash;
>  #endif
> +       u16                     sk_incoming_cpu;
> +       /* 16bit hole
> +        * Warned : sk_incoming_cpu can be set from softirq,
> +        * Do not use this hole without fully understanding possible issues.
> +        */
> +
>         __u32                   sk_txhash;
>  #ifdef CONFIG_NET_RX_BUSY_POLL
>         unsigned int            sk_napi_id;
> @@ -833,6 +840,11 @@ static inline int sk_backlog_rcv(struct sock *sk, struct sk_buff *skb)
>         return sk->sk_backlog_rcv(sk, skb);
>  }
>
> +static inline void sk_incoming_cpu_update(struct sock *sk)
> +{
> +       sk->sk_incoming_cpu = raw_smp_processor_id();
> +}
> +
>  static inline void sock_rps_record_flow_hash(__u32 hash)
>  {
>  #ifdef CONFIG_RPS
> diff --git a/include/uapi/asm-generic/socket.h b/include/uapi/asm-generic/socket.h
> index ea0796bdcf88..f541ccefd4ac 100644
> --- a/include/uapi/asm-generic/socket.h
> +++ b/include/uapi/asm-generic/socket.h
> @@ -82,4 +82,6 @@
>
>  #define SO_BPF_EXTENSIONS      48
>
> +#define SO_INCOMING_CPU                49
> +
>  #endif /* __ASM_GENERIC_SOCKET_H */
> diff --git a/net/core/sock.c b/net/core/sock.c
> index 15e0c67b1069..14998b161035 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -1213,6 +1213,10 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
>                 v.val = sk->sk_max_pacing_rate;
>                 break;
>
> +       case SO_INCOMING_CPU:
> +               v.val = sk->sk_incoming_cpu;
> +               break;
> +
>         default:
>                 return -ENOPROTOOPT;
>         }
> @@ -1517,6 +1521,7 @@ struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority)
>
>                 newsk->sk_err      = 0;
>                 newsk->sk_priority = 0;
> +               newsk->sk_incoming_cpu = raw_smp_processor_id();
>                 /*
>                  * Before updating sk_refcnt, we must commit prior changes to memory
>                  * (Documentation/RCU/rculist_nulls.txt for details)
> diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
> index 8893598a4124..2c6a955fd5c3 100644
> --- a/net/ipv4/tcp_ipv4.c
> +++ b/net/ipv4/tcp_ipv4.c
> @@ -1663,6 +1663,7 @@ process:
>         if (sk_filter(sk, skb))
>                 goto discard_and_relse;
>
> +       sk_incoming_cpu_update(sk);
>         skb->dev = NULL;
>
>         bh_lock_sock_nested(sk);
> diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> index cd0db5471bb5..52235ca1f352 100644
> --- a/net/ipv4/udp.c
> +++ b/net/ipv4/udp.c
> @@ -1445,6 +1445,7 @@ static int __udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
>         if (inet_sk(sk)->inet_daddr) {
>                 sock_rps_save_rxhash(sk, skb);
>                 sk_mark_napi_id(sk, skb);
> +               sk_incoming_cpu_update(sk);
>         }
>
>         rc = sock_queue_rcv_skb(sk, skb);
> diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
> index fd8e50b380e7..1985b4933a6b 100644
> --- a/net/ipv6/tcp_ipv6.c
> +++ b/net/ipv6/tcp_ipv6.c
> @@ -1456,6 +1456,7 @@ process:
>         if (sk_filter(sk, skb))
>                 goto discard_and_relse;
>
> +       sk_incoming_cpu_update(sk);
>         skb->dev = NULL;
>
>         bh_lock_sock_nested(sk);
> diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
> index f6ba535b6feb..2c7790c9ac65 100644
> --- a/net/ipv6/udp.c
> +++ b/net/ipv6/udp.c
> @@ -577,6 +577,7 @@ static int __udpv6_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
>         if (!ipv6_addr_any(&sk->sk_v6_daddr)) {
>                 sock_rps_save_rxhash(sk, skb);
>                 sk_mark_napi_id(sk, skb);
> +               sk_incoming_cpu_update(sk);
>         }
>
>         rc = sock_queue_rcv_skb(sk, skb);
> diff --git a/net/sctp/ulpqueue.c b/net/sctp/ulpqueue.c
> index d49dc2ed30ad..ce469d648ffb 100644
> --- a/net/sctp/ulpqueue.c
> +++ b/net/sctp/ulpqueue.c
> @@ -205,9 +205,10 @@ int sctp_ulpq_tail_event(struct sctp_ulpq *ulpq, struct sctp_ulpevent *event)
>         if (sock_flag(sk, SOCK_DEAD) || (sk->sk_shutdown & RCV_SHUTDOWN))
>                 goto out_free;
>
> -       if (!sctp_ulpevent_is_notification(event))
> +       if (!sctp_ulpevent_is_notification(event)) {
>                 sk_mark_napi_id(sk, skb);
> -
> +               sk_incoming_cpu_update(sk);
> +       }
>         /* Check if the user wishes to receive this event.  */
>         if (!sctp_ulpevent_is_enabled(event, &sctp_sk(sk)->subscribe))
>                 goto out_free;
> --
> 2.1.0.rc2.206.gedb03e5
>
> --
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-- 
Michael Kerrisk Linux man-pages maintainer;
http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface", http://blog.man7.org/
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