Re: [patch] add optimized generic percpu accessors

[Ingo Molnar]

* Tejun Heo <tj@xxxxxxxxxx> wrote:

> roel kluin wrote:
> >> Index: linux/include/asm-generic/percpu.h
> >> ===================================================================
> >> --- linux.orig/include/asm-generic/percpu.h
> >> +++ linux/include/asm-generic/percpu.h
> >> @@ -80,4 +80,32 @@ extern void setup_per_cpu_areas(void);
> >>  #define DECLARE_PER_CPU(type, name) extern PER_CPU_ATTRIBUTES \
> >>                                        __typeof__(type) per_cpu_var(name)
> >>
> >> +/*
> >> + * Optional methods for optimized non-lvalue per-cpu variable access:
> >> + */
> >> +
> >> +#ifndef percpu_read
> >> +# define percpu_read(var)              __get_cpu_var(var)
> >> +#endif
> >> +
> >> +#ifndef percpu_write
> >> +# define percpu_write(var, val)                ({ __get_cpu_var(var) = (val); })
> >> +#endif
> >> +
> >> +#ifndef percpu_add
> >> +# define percpu_add(var, val)          ({ __get_cpu_var(var) += (val); })
> >> +#endif
> >> +
> >> +#ifndef percpu_sub
> >> +# define percpu_add(var, val)          ({ __get_cpu_var(var) += (val); })
> > 
> > this should be:
> > 
> > define percpu_sub(var, val)          ({ __get_cpu_var(var) -= (val); })

well spotted!

> Thanks.  Will fold into the patch.

thanks!

Is there any interim tree for us to pull into -tip? I'd rather not let 
this grow too big, it will be harder and harder to debug any regressions. 
Gradual progress is a lot more debuggable. Your initial patchset is 
fantastic already (gives a ~0.2% kernel image size saving for defconfig), 
so it's a very good start.

	Ingo
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