Messages in this thread | | | Date | Wed, 28 Sep 2011 15:19:50 -0300 | From | Glauber Costa <> | Subject | Re: [RFD 1/9] Change cpustat fields to an array. |
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On 09/27/2011 06:00 PM, Peter Zijlstra wrote: > On Fri, 2011-09-23 at 19:20 -0300, Glauber Costa wrote: >> /* Must have preemption disabled for this to be meaningful. */ >> -#define kstat_this_cpu __get_cpu_var(kstat) >> +#define kstat_this_cpu this_cpu_ptr(task_group_kstat(current)) > > This just lost you a debug check, the former would whinge when called > without preemption, the new one wont. Its part of the this_cpu feature > set to make debugging impossible. > >> +#else >> +#define kstat_cpu(cpu) per_cpu(kstat, cpu) >> +#define kstat_this_cpu (&__get_cpu_var(kstat)) >> +#endif >> >> extern unsigned long long nr_context_switches(void); >> >> @@ -52,8 +62,8 @@ struct irq_desc; >> static inline void kstat_incr_irqs_this_cpu(unsigned int irq, >> struct irq_desc *desc) >> { >> - __this_cpu_inc(kstat.irqs[irq]); >> - __this_cpu_inc(kstat.irqs_sum); >> + kstat_this_cpu->irqs[irq]++; >> + kstat_this_cpu->irqs_sum++; > > It might be worth looking at the asm output of that, I think you made it > worse, but I'm not quite sure how smart gcc is, it might just figure out > what you meant.
I'd say leave it alone. The biggest difference is that we don't have access to task_group(), or any of the fields in struct task_group. Because of that, we end up having to export a function to do the job of dealing with it.
Users inside sched.c won't have this problem. Outside of it, we'll add a call to some paths. True, mostly handle_irq paths, but I don't think that's what's going to kill us.
Now if we really really want to save it, we'd have to move struct task_group and its friends to a more visible location like a header...
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