Re: [PATCH net-next] net: skbuff: Skip early return in skb_unref when debugging

[Paolo Abeni]

On 7/30/24 16:10, Jakub Kicinski wrote:
> On Tue, 30 Jul 2024 13:15:57 +0200 Paolo Abeni wrote:
> > > I was under impression that entire reason for CONFIG_DEBUG_NET was
> > > to enable more checks for fuzzers and the like, i.e. NOT for production
> > > kernels.
> >
> > I feel like I already had this discussion and I forgot the outcome, if
> > so I'm sorry. To me the "but is safe to select." part in the knob
> > description means this could be enabled in production, and AFAICS the
> > CONFIG_DEBUG_NET-enabled code so far respects that assumption.
>
> I believe the previous discussion was page pool specific and there
> wasn't as much of a conclusion as an acquiescence (read: we had more
> important things on our minds than that argument ;)).
>
> Should we set a bar for how much perf impact is okay?

I think that better specifying the general guidance/expectation should 
be enough. What about extending the knob description with something alike:
---
diff --git a/net/Kconfig.debug b/net/Kconfig.debug
index 5e3fffe707dd..058cf031913b 100644
--- a/net/Kconfig.debug
+++ b/net/Kconfig.debug
@@ -24,3 +24,5 @@ config DEBUG_NET
        help
          Enable extra sanity checks in networking.
          This is mostly used by fuzzers, but is safe to select.
+         This could introduce some very minimal overhead and
+         is not suggested for production systems.