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smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=W6kuST3N; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 453F9606A31C for ; Wed, 11 Nov 2026 13:08:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=W6kuST3N Received: by smtp.kernel.org (Postfix) with ESMTPSA id 536EF1F00A05; Wed, 11 Nov 2026 13:08:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794402524; bh=tpSt5JkGUaHCP8XlikkEOI4qJddO1S2MUXWY1pm1gq8=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=W6kuST3NNP4zzA9PqmXm/bYJ6yoRhEgKl5fNUQn6dha9mMZiyvNhUUICtqwe3+ArG jrSjuVs6BfBQGx22OPJQDQ77+zIoHH2HjoU2ZvMA72U2kcHSkaIJPXdd7WX8Q6lU23 BvsgBMhjHnKrtcDHA0gHVEVcKkuv7cyNUTCCbadw4goRnxkbFWPRAj5QxKya1CySU1 vhoM+ye5tViT7u0sZFpSC8q3yi9BbrZSS0jKAptLmf2YYRwMsQ1ePzHf2uCedCXW4f /KreGp+leeCIRPhMfpge9Ms4JosjH+/kYUEU1/2xKHMyvkoAXWxY72zws1fLN5KnlT mk5wUibYF1QZg== Message-ID: Date: Wed, 11 Nov 2026 14:08:40 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/slab: don't set SLAB_MAY_ACCOUNT for KMALLOC_PARTITION_CACHES Content-Language: en-US To: Hao Li , harry@kernel.org, akpm@linux-foundation.org Cc: cl@gentwo.org, rientjes@google.com, roman.gushchin@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Suren Baghdasaryan References: <20261111125628.375624-1-hao.li@linux.dev> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/11/26 13:49, Hao Li wrote: > An allocation with __GFP_ACCOUNT set (without __GFP_DMA or > __GFP_RECLAIMABLE) is redirected to KMALLOC_CGROUP and will never hit > KMALLOC_NORMAL or KMALLOC_PARTITION_CACHES. Consequently, neither of > these caches requires objcg slots in obj_exts. > > While KMALLOC_NORMAL already skips setting SLAB_MAY_ACCOUNT, > KMALLOC_PARTITION_CACHES still carries it unnecessarily. > > Extend the check to skip KMALLOC_PARTITION_CACHES as well, saving > unnecessary objcg slots in obj_exts. > > Signed-off-by: Hao Li Reviewed-by: Vlastimil Babka (SUSE) > --- > This doesn't seem like a real bug to me, just a small waste of memory, so I > didn't add a Fixes tag. Hmm I'd add Fixes: 7def2e8549e5 ("mm/slab: add cache_ and slab_needs_objcg() helpers") The question is whether cc stable as well. 7.3 LTS will be used for Android and IIRC they have memory allocation profiling enabled. Not sure about kmalloc partitions. Cc'ing Suren. > --- > mm/slab_common.c | 10 ++++++---- > 1 file changed, 6 insertions(+), 4 deletions(-) > > diff --git a/mm/slab_common.c b/mm/slab_common.c > index 2befd24b4d09..f0ea1fa178e7 100644 > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -1000,16 +1000,18 @@ new_kmalloc_cache(int idx, enum kmalloc_cache_type type) > #endif > > /* > - * If memcg_kmem is enabled and this is a KMALLOC_NORMAL cache and not > - * aliased with any other type, make sure it's never merged with any other > - * cache. > + * If memcg_kmem is enabled and this is a KMALLOC_NORMAL or > + * KMALLOC_PARTITION_CACHES cache and not aliased with any other type, > + * make sure it's never merged with any other cache. > * > * In other cases the kmalloc cache may end up being used for a > * __GFP_ACCOUNT allocation so mark it as such. The exception is a > * KMALLOC_NO_OBJ_EXT cache. > */ > if (!mem_cgroup_kmem_disabled()) { > - if (type == KMALLOC_NORMAL && KMALLOC_RECLAIM != KMALLOC_NORMAL) > + if (type >= KMALLOC_PARTITION_START && > + type <= KMALLOC_PARTITION_END && > + KMALLOC_RECLAIM != KMALLOC_NORMAL) > flags |= SLAB_NO_MERGE; > else if (!(flags & SLAB_NO_OBJ_EXT)) > flags |= SLAB_MAY_ACCOUNT;