Re: [PATCH] mm/slub: serve slabobj_ext array from a strictly larger kmalloc cache

[Harry Yoo <harry@kernel.org>]

On 7/1/26 4:42 PM, Harry Yoo wrote:
> 
> 
> On 7/1/26 1:53 PM, Harry Yoo wrote:
>>
>>
>> On 7/1/26 1:30 PM, Harry Yoo wrote:
>>> We can do that in pre-7.2 kernels, by teaching kmalloc_type() and
>>> kmalloc_slab() select the new KMALLOC_TYPE based on __GFP_NO_OBJ_EXT?
>>>
>>> e.g.) Select the new KMALLOC_TYPE when KMALLOC_NOT_NORMAL_BITS is not
>>> set AND __GFP_NO_OBJ_EXT is set.
>>
>> Uh, this is bit subtle though.
>>
>> In some cases  KMALLOC_DMA == KMALLOC_NORMAL,
>> KMALLOC_CGROUP == KMALLOC_NORMAL,
>> or KMALLOC_RECLAIM == KMALLOC_NORMAL.
>>
>> Just checking KMALLOC_NOT_NORMAL_BITS is misleading.
> 
> Here's a prototype for slab/for-next. Backporting it requires handling
> __GFP_NO_OBJ_EXT instead of SLAB_ALLOC_NO_RECURSE, but shouldn't be
> too difficult. Now writing changelog and going through testing...

Now thinking about the performance implication of sheaf allocations
for kmalloc caches being served from KMALLOC_NO_RECURSE caches won't
have sheaves at all

-- 
Cheers,
Harry / Hyeonggon