netdev - Re: [PATCH net] net: increase SOMAXCONN to 4096

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Date:   Thu, 31 Oct 2019 05:35:41 +0100
From:   Willy Tarreau <w@....eu>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Neal Cardwell <ncardwell@...gle.com>,
        Yuchung Cheng <ycheng@...gle.com>, Yue Cao <ycao009@....edu>
Subject: Re: [PATCH net] net: increase SOMAXCONN to 4096

On Wed, Oct 30, 2019 at 08:46:26PM -0700, Eric Dumazet wrote:
> On Wed, Oct 30, 2019 at 8:36 PM Willy Tarreau <w@....eu> wrote:
> > Just a quick question, I remember that when somaxconn is greater than
> > tcp_max_syn_backlog, SYN cookies are never emitted, but I think it
> > recently changed and there's no such constraint anymore. Do you
> > confirm it's no more needed, or should we also increase this latter
> > one accordingly ?
> >
> 
> There is no relationship like that.
> 
> The only place somaxconn is use is in __sys_listen() to cap the
> user-provided backlog.
> 
> somaxconn = sock_net(sock->sk)->core.sysctl_somaxconn;
> if ((unsigned int)backlog > somaxconn)
>        backlog = somaxconn;

OK, thanks for checking.

Willy