Re: [PATCH] Cpuset: rcu optimization of page alloc hook

[Eric Dumazet <dada1@cosmosbay.com>]

Nick Piggin a écrit :
> Eric Dumazet wrote:
>
> > Paul Jackson a écrit :
> >
> > > +
> > > +static kmem_cache_t *cpuset_cache;
> > > +
> >
> >
> >
> > Hi Paul
> >
> > Please do use __read_mostly for new kmem_cache :
> >
> > static kmem_cache_t *cpuset_cache __read_mostly;
> >
> > If not, the pointer can sit in the midle of a highly modified cache 
> > line, and multiple CPUS will have memory cache misses to access the 
> > cpuset_cache, while slab code/data layout itself is very NUMA/SMP 
> > friendly.
>
> Is it a good idea for all kmem_cache_t? If so, can we move
> __read_mostly to the type definition?

Well this question was already asked.

You cannot move __read_mostly to the type itself as some kmem_cache_t are 
included in some data structures.

struct {
 ...
 kmem_cache_t *slab;
 ...
};

And in this case you cannot automatically add __read_mostly

Eric
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