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Date: Fri, 3 Apr 2026 20:29:22 +0200
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Subject: Re: [PATCH v1] slab: support for compiler-assisted type-based slab
 cache partitioning
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To: "Harry Yoo (Oracle)" <harry@kernel.org>, Marco Elver <elver@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
 Nathan Chancellor <nathan@kernel.org>, Nicolas Schier <nsc@kernel.org>,
 Dennis Zhou <dennis@kernel.org>, Tejun Heo <tj@kernel.org>,
 Christoph Lameter <cl@gentwo.org>, Hao Li <hao.li@linux.dev>,
 David Rientjes <rientjes@google.com>,
 Roman Gushchin <roman.gushchin@linux.dev>, Kees Cook <kees@kernel.org>,
 "Gustavo A. R. Silva" <gustavoars@kernel.org>,
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 "Liam R. Howlett" <Liam.Howlett@oracle.com>, Mike Rapoport
 <rppt@kernel.org>, Suren Baghdasaryan <surenb@google.com>,
 Michal Hocko <mhocko@suse.com>, Alexander Potapenko <glider@google.com>,
 Dmitry Vyukov <dvyukov@google.com>,
 Nick Desaulniers <nick.desaulniers+lkml@gmail.com>,
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 linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
 linux-mm@kvack.org, linux-hardening@vger.kernel.org,
 kasan-dev@googlegroups.com, llvm@lists.linux.dev,
 Andrey Konovalov <andreyknvl@gmail.com>, Florent Revest <revest@google.com>,
 GONG Ruiqi <gongruiqi@huaweicloud.com>, Jann Horn <jannh@google.com>,
 KP Singh <kpsingh@kernel.org>, Matteo Rizzo <matteorizzo@google.com>
References: <20260331111240.153913-1-elver@google.com>
 <ac9d5O5XehnXRc5A@hyeyoo>
From: "Vlastimil Babka (SUSE)" <vbabka@kernel.org>
In-Reply-To: <ac9d5O5XehnXRc5A@hyeyoo>
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On 4/3/26 08:27, Harry Yoo (Oracle) wrote:
>> diff --git a/include/linux/slab.h b/include/linux/slab.h
>> index 15a60b501b95..c0bf00ee6025 100644
>> --- a/include/linux/slab.h
>> +++ b/include/linux/slab.h
>> @@ -864,10 +877,10 @@ unsigned int kmem_cache_sheaf_size(struct slab_sheaf *sheaf);
>>   * with the exception of kunit tests
>>   */
>>  
>> -void *__kmalloc_noprof(size_t size, gfp_t flags)
>> +void *__kmalloc_noprof(size_t size, gfp_t flags, kmalloc_token_t token)
>>  				__assume_kmalloc_alignment __alloc_size(1);
>>  
>> -void *__kmalloc_node_noprof(DECL_BUCKET_PARAMS(size, b), gfp_t flags, int node)
>> +void *__kmalloc_node_noprof(DECL_BUCKET_PARAMS(size, b), gfp_t flags, int node, kmalloc_token_t token)
>>  				__assume_kmalloc_alignment __alloc_size(1);
> 
> So the @token parameter is unused when CONFIG_PARTITION_KMALLOC_CACHES is
> disabled but still increases the kernel size by a few kilobytes...
> but yeah I'm not sure if we can get avoid it without hurting readability.
> 
> Just saying. (does anybody care?)

Well we did care enough with CONFIG_SLAB_BUCKETS to hide the unused param
using DECL_BUCKET_PARAMS(), so maybe extend that idea?
I think it's not just kernel size, but increased register pressure etc.