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b=cy6kjQFkF4jpcqM44CdJdI/SbntqMzc47zdacoBocnMIE+RSA+Yir8eEMGdL9vCJy cBNICFcr6ytzPrJPd6sMffkPGMU2+zvaXrYChZLUigJ1PXdouprajqfuCEho/05zmJ g4cVaMJ456kQZ0GnQrQtXMN0a8DBtFIDgm16hF7OOE+pvUUVENNys5oIeGP7JnFkKa y55XbkMCTid2VAdZnPiIRmaSzkXjjYb9jYTMlB3pUdtEgtiBUupysiRM8ZksGt1x+6 5Eti5wswN2scSv0+4RnPEF0UUn4P5UmdFhuwo6jVqBMOAEnXlU/3mvuIwdEbTY922G 4rIdHY+9KX39g== Date: Wed, 22 Apr 2026 11:36:26 +0300 From: Mike Rapoport To: Sang-Heon Jeon Cc: akpm@linux-foundation.org, djbw@kernel.org, mingo@kernel.org, linux-mm@kvack.org, Donghyeon Lee , Munhui Chae Subject: Re: [PATCH v2] mm/fake-numa: fix under-allocation detection in uniform split Message-ID: References: <20260417135805.1758378-1-ekffu200098@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Server: rspam10 X-Stat-Signature: p7m4mtb567in198fpgig64184ztxpu4p X-Rspam-User: X-Rspamd-Queue-Id: 0FF22C000D X-HE-Tag: 1776846993-751590 X-HE-Meta: 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 QIv/Et1A t9iaEtbQkGCsYioPeRW+rSMrGKWBC9dkzqI0+1/aRafl0I3jCWohF21LYYGtM+ljS4VSnRED0QchZ5EhNFKOsTJaK5Zos1wB2MRq/VuWg5PaKbJBZPY8dJPnr1dDFLgmYo3iQOoccWU5aQya5k8xSkWnYVDfAd2CulPHdLxtnSoIfoHVyTK0cak1nb2nz92vypirIYqSbjqQ6rWhc3sYyWyaVBlKBev8FFVXFIRsTi/G9dsAna1W8DvGhjINTuw203ovECKl69/O6fdR/rKVMCSPiBOFiXbHW2qpPAJ02seUBw78= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Apr 21, 2026 at 03:56:01PM +0900, Sang-Heon Jeon wrote: > Hi > > On Tue, Apr 21, 2026 at 3:29 PM Mike Rapoport wrote: > > > > On Mon, Apr 20, 2026 at 11:26:13PM +0900, Sang-Heon Jeon wrote: > > > On Mon, Apr 20, 2026 at 3:31 PM Mike Rapoport wrote: > > > > On Fri, Apr 17, 2026 at 10:58:05PM +0900, Sang-Heon Jeon wrote: > > > > > When split NUMA node uniformly, split_nodes_size_interleave_uniform() > > > > > returns the next absolute node ID, not the number of nodes created. > > > > > > > > > > The existing under-allocation detection logic compares next absolute node > > > > > ID (ret) and request count (n), which only works when nid starts at 0. > > > > > > > > > > For example, on a system with 2 physical NUMA nodes (node 0: 2GB, node > > > > > 1: 128MB) and numa=fake=8U, 8 fake nodes are successfully created from > > > > > node 0 and split_nodes_size_interleave_uniform() returns 8. For node 1, > > > > > fake node nid starts at 8, but only 4 fake nodes are created due to > > > > > current FAKE_NODE_MIN_SIZE being 32MB, and > > > > > split_nodes_size_interleave_uniform() returns 12. By existing > > > > > under-allocation detection logic, "ret < n" (12 < 8) is false, so the > > > > > > > > In this example it would be 11, won't it? > > > > I'll update when applying. > > > > > > Oops, my previous reply is not the main point of this review. (Please ignore it) > > > But 12 is still correct, because split_nodes_size_interleave_uniform() > > > returns next available node ID. > > > > > > IMHO, it would be clearer if both the commit message and the function > > > comment change into "next available node ID". > > > If you're okay with it, I'll create v3 patch soon, including minor fix below > > > > No need for v3, I updated the comment and the whitespace: > > https://git.kernel.org/rppt/memblock/c/a34436ac05e76bd6634a89fc0a399ab3a48f509a > > Thanks for your help, Mike. However, it seems like '12' was changed to > '11' in the commit message. I think this change should be rolled back. > Could you check? Node IDs are counted from 0, hence for 12 nodes the last nid would be 11. -- Sincerely yours, Mike.