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b=OhEYI6eOjzLMVTpBUMc6V2EolP/jAuhojRfnyLjJoIYYyzJiWjWXX36/RLXUslYOd YTuJZ6lKQgWGKAjsuqoVU7eQQoUg4vZhI+MAnuqusMrwy1vE74KeSqIY72QmPuctYp nrU1d+XY/tm1BicogkivFEqYOpw8xtFYffn+RJfOgxxogiqCElg3ZnaBiwUbuK/VEL VlHL5lbRsW2JUp0a8wEn/hRELPcv+koJjY7d0Bfcdjtf8I/nt5otijl1bz1MdKCbkC ozXqmfHGZd/hVjmPXCghC+oZj72/Uke3GH/AUEJ8uSaG06o2yBkXEG8lqs5nM93msm kITseR2zVcgbw== Date: Tue, 21 Apr 2026 09:29:17 +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-Stat-Signature: 4eiremr6zyenpwm3nkhn83tno4ct4rjq X-Rspamd-Queue-Id: 4C9BE1C0004 X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1776752964-542521 X-HE-Meta: U2FsdGVkX1/9PRh/qK/lCbYlAA1R84R46NSfgWgP/OCs43LlEbGDsknqJYLvccoUdXSBBn5P3KocRLfS5ARJtljKH11oqKJrDVf6nGGWPhL9q4zyxQlrjJIisuG37NObFCQQye7md/+lGstigIEck93hc2r8jFGXlqiRm1A+zoDvsRECrU/Q11wc2Shi2/bsBMAftiihJc/4MTnoWm0FyAFFNzF38t8FtNSm+O/6TbZYFet5uzko3LTeo/06DLygMuD43GHyyWbk+iSz0EK9tAznaeAKbuBZKBsMTrDgnNb3puhTQSX7W3oT7+d/p8r0plxvfHRvqrju4PwVzJ2zCSYl14b59U5u6ZeBpzhoie8zfnLawI+rWFopCc6IJVGefpBv/lhYS0dRH4w4AppHhsIxmq6BKTyzdLfRYtgA/fO2h/KXlGoa9f1Dyv3mEHRzm71n0sHcdz/jADJhJtjv4gLZwM3rlUPC1nMRr5s7E8kyb/+cFGzixLbfsKV+uK6UdEh436Dw3Om1G6m9XrxEyi+2PhgETCk8pogieAcwCHEc2Ky0YVEjiktymDDicQxxAy+OjQFzsuUXuAi4SyeIDHhiTcA0xLQtOAGyNlSghRmCX/Whd33Ve1D12k9g54iLKgAXGdoKBlHL/CLFDx0dM2XGken9j/hpCOkldzjqUjXUgXk2tThadAlRcYCBhXyYsYz4eYte7kmsTfyGpijGm8haGwyGhOIdlAKMLhsEMV9jW5beLZMnvOOyNQ9P7IX6tpd6sjYh4tC8JatSEUNloL7kPggF+a8xwMBmrNlhZZoPNIvuHf4rVh2jBdyUXB6Z0KKf6IqCJNS6AorWcUS4t5UQrCDVbN2lZuItC3CXcW7mtoQXLCML8pWbzPL1c0PBAyQsLcQP0TbGonLhLw5mFrc6htVYV3L4+oPj5hMe7j/xp98Hwtpr9+1y4085F95O6JAQeIBjcG1xDUmXxzM MaWhlcsw NxzRh/bH/SS8kIkFVs6s/6P3ZrwPdg4jthQ2ZXpIbSzcp1vGsCRbAbKlPTKCTSptvs0hyTNhpSbxZOQSwsVQjok0tAub0MGkFgaYphmJA43XjP9qspMkmDN0adcQ8a1BTT26fUOk7b6wOoPLAXmdXl92br78geCZw+GN7sxY90C34Zj/JLemVL/4RfStZCtKr9Od9kW7yuuL22z4uWI/LqnjHK03oEhWhLXB0GPcLwIacvpo5uvUpihh3S7G2TCi/gYGmDOSySGcK4OxJQ44kqZns9+E9L9hdv1gzsacxBFP1R9U= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 > Best Regards, > Sang-Heon Jeon -- Sincerely yours, Mike.