Re: [PATCH net-next v3] net: skb: isolate skb data area allocations into a separate bucket

[Harry Yoo <harry@kernel.org>]

On 7/8/26 8:16 PM, Pedro Falcato wrote:
> On Wed, Jul 08, 2026 at 10:30:50AM +0200, Paolo Abeni wrote:
>> On 7/2/26 7:07 PM, Pedro Falcato wrote:> @@ -586,6 +586,8 @@ struct
>> sk_buff *napi_build_skb(void *data, unsigned int frag_size)
>>>  }
>>>  EXPORT_SYMBOL(napi_build_skb);
>>>  
>>> +static kmem_buckets *skb_data_buckets __ro_after_init;
>>> +
>>>  static void *kmalloc_pfmemalloc(size_t obj_size, gfp_t flags, int node)
>>>  {
>>>  	if (!gfp_pfmemalloc_allowed(flags))
>>> @@ -593,7 +595,8 @@ static void *kmalloc_pfmemalloc(size_t obj_size, gfp_t flags, int node)
>>>  	if (!obj_size)
>>>  		return kmem_cache_alloc_node(net_hotdata.skb_small_head_cache,
>>>  					     flags, node);
>>> -	return kmalloc_node_track_caller(obj_size, flags, node);
>>> +	return kmem_buckets_alloc_node_track_caller(skb_data_buckets, obj_size,
>>> +						    flags, node);
>>
>> Sashiko noted that some drivers may require GFP_DMA buckets, and the
>> above may break them:
>>
>> https://sashiko.dev/#/patchset/20260702170728.168755-1-pfalcato%40suse.de
> 
> Oh, this is really awkward. Adding linux-mm and slab maintainers for input here.
> 
> Considering the current slab bucketing does not seem to duplicate DMA or
> CGROUP caches, could it make sense to duplicate those as well?

Could we specify what kmalloc types the user needs when creating
kmem_buckets and duplicate caches for the requested kmalloc types only?

> Otherwise we could add a branch like:
>
> if (gfp_flags & __GFP_DMA)
> 	/* use the global dma kmalloc caches */

-- 
Cheers,
Harry / Hyeonggon