Subject: Re: [PATCH v3 net-next 0/4] tcp: better smp listener behavior

From: Grant Zhang <[email-masked]>
Date: Thu, 8 Oct 2015 21:16:38 -0700

On 08/10/2015 19:33, Eric Dumazet wrote:
> As promised in last patch series, we implement a better SO_REUSEPORT
> strategy, based on cpu affinities if selected by the application.
>
> We also moved sk_refcnt out of the cache line containing the lookup
> keys, as it was considerably slowing down smp operations because
> of false sharing. This was simpler than converting listen sockets
> to conventional RCU (to avoid sk_refcnt dirtying)
>
> Could process 6.0 Mpps SYN instead of 4.2 Mpps on my test server.
>
> Eric Dumazet (4):
>    net: SO_INCOMING_CPU setsockopt() support
>    net: align sk_refcnt on 128 bytes boundary
>    net: shrink struct sock and request_sock by 8 bytes
>    tcp: shrink tcp_timewait_sock by 8 bytes
>
>   include/linux/tcp.h              |  4 ++--
>   include/net/inet_timewait_sock.h |  2 +-
>   include/net/request_sock.h       |  7 +++----
>   include/net/sock.h               | 41 +++++++++++++++++++++++++++-------------
>   net/core/sock.c                  |  5 +++++
>   net/ipv4/inet_hashtables.c       |  2 ++
>   net/ipv4/syncookies.c            |  4 ++--
>   net/ipv4/tcp_input.c             |  2 +-
>   net/ipv4/tcp_ipv4.c              |  2 +-
>   net/ipv4/tcp_minisocks.c         | 18 +++++++++---------
>   net/ipv4/tcp_output.c            |  2 +-
>   net/ipv4/udp.c                   |  6 +++++-
>   net/ipv6/inet6_hashtables.c      |  2 ++
>   net/ipv6/syncookies.c            |  4 ++--
>   net/ipv6/tcp_ipv6.c              |  2 +-
>   net/ipv6/udp.c                   | 11 +++++++----
>   16 files changed, 72 insertions(+), 42 deletions(-)
>
Eric,

Does it make sense to make the listener hash table percpu? Socket with 
SO_INCOMING_CPU set could just be add to the hashtable for that specific 
cpu.

Thanks,

Grant