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