Messages in this thread | | | From | Arjan van de Ven <> | Date | Tue, 14 Jun 2016 10:14:29 -0700 | Subject | Re: [patch 13/20] timer: Switch to a non cascading wheel |
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evaluating a 120 hours timer ever 37 hours to see if it should fire... not too horrid.
On Tue, Jun 14, 2016 at 9:28 AM, Thomas Gleixner <tglx@linutronix.de> wrote: > On Tue, 14 Jun 2016, Ingo Molnar wrote: >> * Thomas Gleixner <tglx@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
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