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Re: [PATCH ipvs-next] ipvs: count pre-established TCP states as active

To: Michal Kubecek <mkubecek@xxxxxxx>
Subject: Re: [PATCH ipvs-next] ipvs: count pre-established TCP states as active
Cc: lvs-devel@xxxxxxxxxxxxxxx, Wensong Zhang <wensong@xxxxxxxxxxxx>, Simon Horman <horms@xxxxxxxxxxxx>, netfilter-devel@xxxxxxxxxxxxxxx, coreteam@xxxxxxxxxxxxx, netdev@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>, Patrick McHardy <kaber@xxxxxxxxx>, Jozsef Kadlecsik <kadlec@xxxxxxxxxxxxxxxxx>, "David S. Miller" <davem@xxxxxxxxxxxxx>
From: Julian Anastasov <ja@xxxxxx>
Date: Sun, 12 Jun 2016 18:27:39 +0300 (EEST)
        Hello,

On Fri, 3 Jun 2016, Michal Kubecek wrote:

> Some users observed that "least connection" distribution algorithm doesn't
> handle well bursts of TCP connections from reconnecting clients after
> a node or network failure.
> 
> This is because the algorithm counts active connection as worth 256
> inactive ones where for TCP, "active" only means TCP connections in
> ESTABLISHED state. In case of a connection burst, new connections are
> handled before previous ones have finished the three way handshaking so
> that all are still counted as "inactive", i.e. cheap ones. The become
> "active" quickly but at that time, all of them are already assigned to one
> real server (or few), resulting in highly unbalanced distribution.
> 
> Address this by counting the "pre-established" states as "active".
> 
> Signed-off-by: Michal Kubecek <mkubecek@xxxxxxx>

Acked-by: Julian Anastasov <ja@xxxxxx>

        Simon, please apply!

> ---
>  net/netfilter/ipvs/ip_vs_proto_tcp.c | 25 +++++++++++++++++++++++--
>  1 file changed, 23 insertions(+), 2 deletions(-)
> 
> diff --git a/net/netfilter/ipvs/ip_vs_proto_tcp.c 
> b/net/netfilter/ipvs/ip_vs_proto_tcp.c
> index d7024b2ed769..5117bcb7d2f0 100644
> --- a/net/netfilter/ipvs/ip_vs_proto_tcp.c
> +++ b/net/netfilter/ipvs/ip_vs_proto_tcp.c
> @@ -395,6 +395,20 @@ static const char *const 
> tcp_state_name_table[IP_VS_TCP_S_LAST+1] = {
>       [IP_VS_TCP_S_LAST]              =       "BUG!",
>  };
>  
> +static const bool tcp_state_active_table[IP_VS_TCP_S_LAST] = {
> +     [IP_VS_TCP_S_NONE]              =       false,
> +     [IP_VS_TCP_S_ESTABLISHED]       =       true,
> +     [IP_VS_TCP_S_SYN_SENT]          =       true,
> +     [IP_VS_TCP_S_SYN_RECV]          =       true,
> +     [IP_VS_TCP_S_FIN_WAIT]          =       false,
> +     [IP_VS_TCP_S_TIME_WAIT]         =       false,
> +     [IP_VS_TCP_S_CLOSE]             =       false,
> +     [IP_VS_TCP_S_CLOSE_WAIT]        =       false,
> +     [IP_VS_TCP_S_LAST_ACK]          =       false,
> +     [IP_VS_TCP_S_LISTEN]            =       false,
> +     [IP_VS_TCP_S_SYNACK]            =       true,
> +};
> +
>  #define sNO IP_VS_TCP_S_NONE
>  #define sES IP_VS_TCP_S_ESTABLISHED
>  #define sSS IP_VS_TCP_S_SYN_SENT
> @@ -418,6 +432,13 @@ static const char * tcp_state_name(int state)
>       return tcp_state_name_table[state] ? tcp_state_name_table[state] : "?";
>  }
>  
> +static bool tcp_state_active(int state)
> +{
> +     if (state >= IP_VS_TCP_S_LAST)
> +             return false;
> +     return tcp_state_active_table[state];
> +}
> +
>  static struct tcp_states_t tcp_states [] = {
>  /*   INPUT */
>  /*        sNO, sES, sSS, sSR, sFW, sTW, sCL, sCW, sLA, sLI, sSA      */
> @@ -540,12 +561,12 @@ set_tcp_state(struct ip_vs_proto_data *pd, struct 
> ip_vs_conn *cp,
>  
>               if (dest) {
>                       if (!(cp->flags & IP_VS_CONN_F_INACTIVE) &&
> -                         (new_state != IP_VS_TCP_S_ESTABLISHED)) {
> +                         !tcp_state_active(new_state)) {
>                               atomic_dec(&dest->activeconns);
>                               atomic_inc(&dest->inactconns);
>                               cp->flags |= IP_VS_CONN_F_INACTIVE;
>                       } else if ((cp->flags & IP_VS_CONN_F_INACTIVE) &&
> -                                (new_state == IP_VS_TCP_S_ESTABLISHED)) {
> +                                tcp_state_active(new_state)) {
>                               atomic_inc(&dest->activeconns);
>                               atomic_dec(&dest->inactconns);
>                               cp->flags &= ~IP_VS_CONN_F_INACTIVE;
> -- 
> 2.8.3

Regards

--
Julian Anastasov <ja@xxxxxx>
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