Messages in this thread | | | Date | Mon, 3 Aug 2015 15:09:39 +0200 | From | Frederic Weisbecker <> | Subject | Re: [PATCH 05/10] nohz: New tick dependency mask |
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On Mon, Aug 03, 2015 at 02:57:17PM +0200, Peter Zijlstra wrote: > On Thu, Jul 23, 2015 at 06:42:10PM +0200, Frederic Weisbecker wrote: > > +void tick_nohz_set_tick_dependency(enum tick_dependency_bit bit) > > +{ > > + unsigned long prev; > > + > > + prev = __tick_nohz_set_tick_dependency(bit, &tick_dependency); > > + if (!prev) > > + tick_nohz_full_kick_all(); > > +} > > > +void tick_nohz_set_tick_dependency_cpu(enum tick_dependency_bit bit, int cpu) > > +{ > > + unsigned long prev; > > + struct tick_sched *ts; > > + > > + ts = per_cpu_ptr(&tick_cpu_sched, cpu); > > + > > + prev = __tick_nohz_set_tick_dependency(bit, &ts->tick_dependency); > > + if (!prev) > > + tick_nohz_full_kick_cpu(cpu); > > +} > > > +/* > > + * Local dependency must have its own flavour due to NMI-safe requirement > > + * on perf. > > + */ > > That doesn't make any sense: > > tick_nohz_set_tick_dependency_this_cpu(); > > (shees, you're nowhere near lazy enough, that's insane to type) is > almost identical to: > > tick_nohz_set_tick_dependency_cpu(.cpu = smp_processor_id()); > > The only difference is a _very_ slight reduction in cost for computing > the per-cpu offset.
But the local one must be NMI-safe. Now I can do:
if (cpu == smp_processor_id()) tick_nohz_full_kick() // NMI-safe else tick_nohz_full_kick_cpu(cpu); // not NMI-safe.
> > > +void tick_nohz_set_tick_dependency_this_cpu(enum tick_dependency_bit bit) > > +{ > > + unsigned long prev; > > + struct tick_sched *ts; > > + > > + ts = this_cpu_ptr(&tick_cpu_sched); > > + > > + prev = __tick_nohz_set_tick_dependency(bit, &ts->tick_dependency); > > + if (!prev) > > + tick_nohz_full_kick(); > > +} > > > And on that naming; could we please shorten them, this is really > ridiculous, it has 'tick' in it twice. > > What's wrong with: > > tick_nohz_set_dep() > tick_nohz_set_dep_cpu()
Right.
Thanks.
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