From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B20F730C174; Tue, 4 Aug 2026 10:29:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785839381; cv=none; b=EK9QC9QA1M1NjtDZRDDfjoO82+xIG/THy3xVZgHSQyUgnKiHHg15EwJTV2jf0JGKNtDDblGCXz+I/4ilogARJ57L0yA7/Lk0horKNkbULmYpa6RMBZuCv+juA8g16MaUH8V8nriZA3bBHAqg4uQk1pJG5endtvrtPblKleAVxws= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785839381; c=relaxed/simple; bh=Z1qnL+ZZnQ9v1yMtnJWYfM7doxw0RU3Zang2vM0k4gE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=GQHfthUWYDRyZTaEYGFKt6ZxtYkXhp9y/OjSPxRtavCfYIKz7/axVGZN7e2FHC6Dkc5VFIbqDq/ZXofSEf8ncqFtDgzRI9sAY8z22ae7TeqSCOhXkB9mMLUIMp3hVYKidkbv0Mat2lg7TFmzVSNg0wOTc1zgP9s7kmEx8LLvUfg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=T8bA1+9W; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="T8bA1+9W" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CC2CB1F000E9; Tue, 4 Aug 2026 10:29:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785839380; bh=5jJUehjbwZzx2iy3C6g3prtNuvVcC8DLucbDRGlti1E=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=T8bA1+9WQXBIZk7Pf43c99bLqvgub+9GyClW3OVH9Ca6OHqZEXpiqGfodxJvnon2E 2KpNejlCJQBLUWNM1xD1XS7+fs6cEi6rOMwCtyrXjAJwPTgDbLAaY+3FNLpVls2pFP eh+CLOOxcqFhmdlfHPCOxsgfGu+w/EkCpKLK/SRfKYYDfHo4yqxFZ5v6UAtjk7kwYy uYrbeJifni3avm1r0vEerQEVWNPOWErt8377C5ApWhowAQBO34DtvXsWre6/eK4nTY S4p292h9vs/YRVwoHlBiuUqtVcucDpkk1Q0vFRTVhw4dK4GGzcaZaGy1pfIG3QfDJu hbsS8h4fKlQ4A== Message-ID: <4feaaba1-258c-4f6c-959c-695b4e62a3dd@kernel.org> Date: Tue, 4 Aug 2026 12:29:35 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 12/13] mm/slab: stop allocating objcg pointers when unnecessary Content-Language: en-US To: Harry Yoo Cc: Suren Baghdasaryan , Hao Li , Shakeel Butt , Alexander Potapenko , Marco Elver , Andrew Morton , Christoph Lameter , David Rientjes , Roman Gushchin , linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org References: <20260727-b4-objext_split-v3-0-c29ef0f1f257@kernel.org> <20260727-b4-objext_split-v3-12-c29ef0f1f257@kernel.org> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/4/26 11:45, Harry Yoo wrote: > On Mon, Jul 27, 2026 at 02:54:06PM +0200, Vlastimil Babka (SUSE) wrote: >> Start using the slab_needs_objcg() helper to calculate slabobj_ext size. >> Caches that we know to never need objcg pointers (currently >> KMALLOC_NORMAL caches) will thus stop wasting memory on them when memory >> allocation profiling is enabled. >> >> For things to work properly, we need to also add slab_needs_objcg() >> checks to mem_cgroup_from_obj_slab() and memcg_slab_free_hook(), because >> when obj_exts array exists for a slab only due to mem_alloc profiling, >> we would otherwise attempt to access a non-existing objcg pointer in >> that slab. >> >> The function __memcg_slab_post_alloc_hook() should not be possible to >> call for a slab where slab_needs_objcg() is false, but add a DEBUG_VM >> check there to prevent breaking this assumption accidentally. > > Perhaps this part is not necessary as slab_obj_ext_set_objcg() now has > a debug warning? Indeed. Removed. Also moved the those debug warnings from 11/13 to here to avoid bisectability issues, as you pointed out offlist. >> >> Reviewed-by: Hao Li >> Signed-off-by: Vlastimil Babka (SUSE) >> --- > > Otherwise LGTM so please feel free to add: > Reviewed-by: Harry Yoo Thanks!