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

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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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