On 3/2/21 5:14 PM, Christoph Lameter wrote:
> On Mon, 10 Aug 2020, Xunlei Pang wrote:
>
>>
>> diff --git a/mm/slab.h b/mm/slab.h
>> index c85e2fa..a709a70 100644
>> --- a/mm/slab.h
>> +++ b/mm/slab.h
>> @@ -616,7 +616,7 @@ struct kmem_cache_node {
>> #ifdef CONFIG_SLUB
>> unsigned long nr_partial;
>> struct list_head partial;
>> - atomic_long_t partial_free_objs;
>> + atomic_long_t __percpu *partial_free_objs;
>
> A percpu counter is never atomic. Just use unsigned long and use this_cpu
> operations for this thing. That should cut down further on the overhead.
>
>> --- a/mm/slub.c
>> +++ b/mm/slub.c
>> @@ -1775,11 +1775,21 @@ static void discard_slab(struct kmem_cache *s,
>> struct page *page)
>> /*
>> * Management of partially allocated slabs.
>> */
>> +static inline long get_partial_free(struct kmem_cache_node *n)
>> +{
>> + long nr = 0;
>> + int cpu;
>> +
>> + for_each_possible_cpu(cpu)
>> + nr += atomic_long_read(per_cpu_ptr(n->partial_free_objs, cpu));
>
> this_cpu_read(*n->partial_free_objs)
>
>> static inline void
>> __update_partial_free(struct kmem_cache_node *n, long delta)
>> {
>> - atomic_long_add(delta, &n->partial_free_objs);
>> + atomic_long_add(delta, this_cpu_ptr(n->partial_free_objs));
>
> this_cpu_add()
>
> and so on.
>
Thanks, I changed them both to use "unsigned long", and will send v3 out
after our internal performance regression test passes.
