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 3BC171DDC2B for ; Tue, 30 Jun 2026 06:12:16 +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=1782799937; cv=none; b=ZLF++73u5h14lPr4lwVYUGa2oRZr4PcnQ3tQphCKo9vpsAhVJTmg9Wg3yva0eFdmrVIKHOiEuErzjD22XiwxoGPQ5Ii/aeY8v8+9uGlOuCqgMnCYjnMP2NhUWFCtB/pfOq/apqA+bLCbnlnYoO/3LYEo67hpIR80gv0tSr0zZoc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782799937; c=relaxed/simple; bh=AsT3z+6d/DwKThx/KImRQ9EU+dZD8UMSnEF5ydPj3dI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=qktcne0ZvbVFEkqMT3QZJGfjZwZF2yynx/z/jTn+pexgki56clfdJt3DsPW4sDKE3VxpTCqAd7IW646NjsHqb75GtdmDs85D/hBiP4CcjrOUAjJKHc6LCEk61rnczEIDr4PkCqj9ASYSKmjkBa6zIJ7FlkXTqA+5Q2wz5eY0x0o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=cUMHmYM9; 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="cUMHmYM9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3B0241F000E9; Tue, 30 Jun 2026 06:12:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782799935; bh=zz7xzpJii4mbLMgFvlEmSOOI69KPmvh9HUemXnItoYI=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=cUMHmYM982w66NfN0Yd1pc4HsLmmFiu4drGcJqOcBxjBuPQw8xt4knvpD4dk2EpAp yp2kitZvdgYmkYOsF35Jq73mayP2sIKDdKKEEIsnP2DCbXnpduVxcZMspnj4+hcDJI d0W1+Zs0RdhGM/Bw7CvvAKTJROoKmNDYxO1GbOyy+phsUiz2Vcr05WMJTPtWMqXoeB WIZKHMVxA1D1cg+SnxOPx0iatbUuLiu6YsSv6zcKOEUnUCuZBLKUtOdCo2W3/KXyRJ I8IJK8eqDMb0ujnHvP1gesJw8wq5I3EPE1F5C2LKFu2HFu7wfVaQMBlDtAhNtqEMVZ gCEl0TD+KtKiQ== Message-ID: Date: Tue, 30 Jun 2026 08:12:11 +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] mm/slub: serve slabobj_ext array from a strictly larger kmalloc cache To: Suren Baghdasaryan , Harry Yoo Cc: Shakeel Butt , Andrew Morton , Roman Gushchin , Hao Li , Christoph Lameter , David Rientjes , Usama Arif , Meta kernel team , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Danielle Costantino , Kees Cook References: <20260625230029.703750-1-shakeel.butt@linux.dev> <62453403-954c-4cf1-8924-6d38184b0810@kernel.org> <09267187-6c85-438f-8791-4cce8d07892a@kernel.org> <68122038-e8e0-47ed-82f8-cb6a23e4658e@kernel.org> <62969830-4b1f-483d-8fa9-9ce487568570@kernel.org> <39a79576-dcae-4b66-9478-c81dfe676699@kernel.org> From: "Vlastimil Babka (SUSE)" Content-Language: en-US Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit On 6/30/26 07:29, Suren Baghdasaryan wrote: > On Mon, Jun 29, 2026 at 9:42 PM Harry Yoo wrote: >> >> >> >> On 6/30/26 1:39 PM, Suren Baghdasaryan wrote: >> > On Mon, Jun 29, 2026 at 9:38 PM Suren Baghdasaryan wrote: >> >> >> >> Ah, here I meant backporting either the kmalloc_flags()+KMALLOC_TYPE or >> SLAB_BUCKETS approach. >> >> >> Yes, it's worth backporting, so we can merge Shakeel's change as is >> >> Right. >> >> >> and then once Vlastimil's patch is merged we can implement the new >> >> Vlastimil's patch has already landed mainline, by the way :) > > Nice! I suggest posting Shakeel's patch CC'ing stable for backports > and then following up with the fix using KMALLOC_TYPE. Vlastimil, > WDYT? Sounded like a plan, but then I realized I misunderstood the amount of the wastage. E.g. on my system kmalloc-8k with 4 objects per slab would have obj_ext size of 64, but now it's 16k? That's ridiculous. I think it will even self-amplify to some extent? kmalloc-8 would have 512 objects per slab, so its obj_ext is 8k. It will not recursively create an obj_ext for the obj_ext, but other 8k allocation in the same kmalloc-8k slab could then trigger it, right? We could say it's for a debugging feature, but also it's running in production fleets (and Android?), so probably not that easy to dismiss. Sudden memory increase in a LTS due to this backport doesn't sound nice to me. >> >> >> KMALLOC_TYPE as a replacement. >> > >> > And Shakeel's patch is easily backportable. >> >> Yes, of course! >> >> -- >> Cheers, >> Harry / Hyeonggon >>