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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 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 X-Stat-Signature: xiyoe76rry78rzjppcdrntp3cbeiku8k X-Rspamd-Queue-Id: CA92440012 X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1782799936-99129 X-HE-Meta: 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 0X8TLhMS KmWT/QTbee6UdGbUEj0elim3WHU+FsL2m3bOcceYrqF0vxMv8/OEeKlI0ItC1f1FPyDGqYKmu/UbZAf4jsIynRgfiV8ZYKcSUDvr5tP4bGLi2WR4LwjDNRTjkQlo0VS+JWg04cu0VlBk+T9mOf1kKXcLkUMXFgjicRMHpKfJJUV6tubQhOUSv2mpSB3Qxdl8cBjXxRkTQUGuRA71Jkjufba1dM8j6tKuugMg5N2OVh6VnbWZmrDStnn/lPRzx2BJxsDnkuxR7Le3+szI9cmw7CFLGH3mMTpRwXxBT3Id2aesdbXNmEhPvcDvNOld1TGF4B2lM4uy7ixzj+AvbJygOO9kuq7SjY8zwwaJKPJmZT00ho6a8KB6BZ6aa0vzM7oSdtXxm Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 >>