On Tue, 14 Jun 2016, Ingo Molnar wrote:
> * Thomas Gleixner <t...@linutronix.de> wrote:
> > On Mon, 13 Jun 2016, Peter Zijlstra wrote:
> > > On Mon, Jun 13, 2016 at 08:41:00AM -0000, Thomas Gleixner wrote:
> > > > +
> > > > + /* Cascading, sigh... */
> > >
> > > So given that userspace has no influence on timer period; can't we
> > > simply fail to support timers longer than 30 minutes?
> > >
> > > In anything really arming timers _that_ long?
> >
> > Unfortunately yes. Networking being one of those. Real cascading happens
> > once
> > in a blue moon, but it happens.
>
> So I'd really prefer it if we added a few more levels, a hard limit and got
> rid of
> the cascading once and for all!
>
> IMHO 'once in a blue moon' code is much worse than a bit more data overhead.
I agree. If we add two wheel levels then we end up with:
HZ 1000: 134217727 ms ~= 37 hours
HZ 250: 536870908 ms ~= 149 hours
HZ 100: 1342177270 ms ~= 372 hours
Looking through all my data I found exactly one timeout which is insanely
large: 120 hours!
That's net/netfilter/nf_conntrack_core.c:
setup_timer(&ct->timeout, death_by_timeout, (unsigned long)ct);
Anything else is way below 37 hours.
Thanks,
tglx
