Re: [PATCH net-next] net: add sysctl to toggle napi_consume_skb() alien skb defer

[Kuniyuki Iwashima <kuniyu@google.com>]

From: Jason Xing <kerneljasonxing@gmail.com>
Date: Fri, 27 Mar 2026 18:37:19 +0800
> On Fri, Mar 27, 2026 at 12:21 AM Jason Xing <kerneljasonxing@gmail.com> wrote:
> ...
> > > Seems a copy/paste of proc_do_static_key() ?
> >
> > Thanks, Eric. Much simpler right now:
> > diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
> > index b508618bfc12..a6a1b2c3f8e1 100644
> > --- a/net/core/sysctl_net_core.c
> > +++ b/net/core/sysctl_net_core.c
> > @@ -676,6 +676,16 @@ static struct ctl_table net_core_table[] = {
> >                 .proc_handler   = proc_do_skb_defer_max,
> >                 .extra1         = SYSCTL_ZERO,
> >         },
> > +       {
> > +               .procname       = "napi_consume_skb_defer",
> > +               .data           = &napi_consume_skb_defer_key.key,
> > +               .maxlen         = sizeof(napi_consume_skb_defer_key),
> > +               .mode           = 0644,
> > +               .proc_handler   = proc_do_static_key,
> > +       },
> >  };
> 
> Eric, when I'm investigating the static key feature, I wonder if we
> can replace some sysctl knob that only carries either 1 or 2 with a
> corresponding static key? The merits are 1) we can minimize the size
> of net.core.xxx or net_hotdata which helps put the structure into one
> cache line, 2) in hot paths, the static key can be more efficient.
> 
> Here is the list that I've found so far:
> 1. sysctl_bypass_prot_mem
> 2. sysctl_tstamp_allow_data
> 3. net_hotdata.tstamp_prequeue
> 4. sysctl_tcp_early_demux
> 5. sysctl_ip_early_demux
> 6. sysctl_tcp_l3mdev_accept
> 7. sysctl_tcp_moderate_rcvbuf
> 8. sysctl_tcp_nometrics_save
> 9. sysctl_tcp_no_ssthresh_metrics_save
> 10. sysctl_tcp_dsack
> 11. sysctl_tcp_abort_on_overflow
> 12. sysctl_tcp_slow_start_after_idle
> 13. sysctl_tcp_timestamps
> ...(some other tcp sysctls)...
> 
> Some of them can be accessed in multiple places, which means they can
> be hot. Maybe we can try some relatively hot knobs first, like
> sysctl_tcp_timestamps, sysctl_tcp_early_demux...? Do you think it's
> feasible?

Note that a static key is only avaiable for global knobs
while most knobs you mentioned above are per-netns.