On 24.8.2015 15:16, Mel Gorman wrote:
>>>
>>> return read_seqcount_retry(¤t->mems_allowed_seq, seq);
>>> @@ -139,7 +141,7 @@ static inline void set_mems_allowed(nodemask_t nodemask)
>>>
>>> #else /* !CONFIG_CPUSETS */
>>>
>>> -static inline bool cpusets_enabled(void) { return false; }
>>> +static inline bool cpusets_mems_enabled(void) { return false; }
>>>
>>> static inline int cpuset_init(void) { return 0; }
>>> static inline void cpuset_init_smp(void) {}
>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>>> index 62ae28d8ae8d..2c1c3bf54d15 100644
>>> --- a/mm/page_alloc.c
>>> +++ b/mm/page_alloc.c
>>> @@ -2470,7 +2470,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
>>> if (IS_ENABLED(CONFIG_NUMA) && zlc_active &&
>>> !zlc_zone_worth_trying(zonelist, z, allowednodes))
>>> continue;
>>> - if (cpusets_enabled() &&
>>> + if (cpusets_mems_enabled() &&
>>> (alloc_flags & ALLOC_CPUSET) &&
>>> !cpuset_zone_allowed(zone, gfp_mask))
>>> continue;
>>
>> Here the benefits are less clear. I guess cpuset_zone_allowed() is
>> potentially costly...
>>
>> Heck, shouldn't we just start the static key on -1 (if possible), so that
>> it's enabled only when there's 2+ cpusets?
Hm wait a minute, that's what already happens:
static inline int nr_cpusets(void)
{
/* jump label reference count + the top-level cpuset */
return static_key_count(&cpusets_enabled_key) + 1;
}
I.e. if there's only the root cpuset, static key is disabled, so I think this
patch is moot after all?
> It's overkill for the amount of benefit.
>
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