On 05/25/2018 05:51 PM, Christopher Lameter wrote:
> On Thu, 24 May 2018, Vlastimil Babka wrote:
>
>> diff --git a/include/linux/slab.h b/include/linux/slab.h
>> index 9ebe659bd4a5..5bff0571b360 100644
>> --- a/include/linux/slab.h
>> +++ b/include/linux/slab.h
>> @@ -296,11 +296,16 @@ static inline void __check_heap_object(const void *ptr, unsigned long n,
>> (KMALLOC_MIN_SIZE) : 16)
>>
>> #ifndef CONFIG_SLOB
>> -extern struct kmem_cache *kmalloc_caches[KMALLOC_SHIFT_HIGH + 1];
>> +extern struct kmem_cache *kmalloc_caches[2][KMALLOC_SHIFT_HIGH + 1];
>> #ifdef CONFIG_ZONE_DMA
>> extern struct kmem_cache *kmalloc_dma_caches[KMALLOC_SHIFT_HIGH + 1];
>> #endif
>
> In the existing code we used a different array name for the DMA caches.
> This is a similar situation.
>
> I would suggest to use
>
> kmalloc_reclaimable_caches[]
>
> or make it consistent by folding the DMA caches into the array too (but
> then note the issues below).
>
>> @@ -536,12 +541,13 @@ static __always_inline void *kmalloc(size_t size, gfp_t flags)
>> #ifndef CONFIG_SLOB
>> if (!(flags & GFP_DMA)) {
>> unsigned int index = kmalloc_index(size);
>> + unsigned int recl = kmalloc_reclaimable(flags);
>
> This is a hotpath reserved for regular allocations. The reclaimable slabs
> need to be handled like the DMA slabs. So check for GFP_DMA plus the
> reclaimable flags.
Yeah I thought that by doing reclaimable via array index manipulation
and not a branch, there would be no noticeable overhead. And GFP_DMA
should go away eventually. I will see if I can convert GFP_DMA to
another index, and completely remove the branch quoted above.
>> @@ -588,12 +594,13 @@ static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
>> if (__builtin_constant_p(size) &&
>> size <= KMALLOC_MAX_CACHE_SIZE && !(flags & GFP_DMA)) {
>> unsigned int i = kmalloc_index(size);
>> + unsigned int recl = kmalloc_reclaimable(flags);
>>
>
>
> Same situation here and additional times below.
>
