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Thu, 17 Sep 2026 10:04:27 +0000 X-Mizu-Trace-ID: 0b148f135692a024 X-Migadu-Flow: FLOW_OUT MIME-Version: 1.0 Date: Thu, 17 Sep 2026 10:04:27 +0000 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable From: "Li Wang" Message-ID: <52d4bc05e867f675fda9f1d5dc34769c10f371c8@linux.dev> TLS-Required: No Subject: Re: [PATCH] mm/hugetlb: account for allowed nodes when gathering surplus pages To: "Huaisheng Ye" , muchun.song@linux.dev, osalvador@suse.de, linux-mm@kvack.org Cc: david@kernel.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, "Huaisheng Ye" In-Reply-To: <20260909074642.7308-1-yehuaisheng@open-hieco.net> References: <20260909074642.7308-1-yehuaisheng@open-hieco.net> X-Stat-Signature: k83k4d1e6k8fki7jjh81siop5chzyoyb X-Rspam-User: X-Rspamd-Queue-Id: A3BEFC0002 X-Rspamd-Server: rspam03 X-HE-Tag: 1789639468-641450 X-HE-Meta: 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 omNbT+Tz 4yQTt+PWWIxnGGv6ILJ7epoMS2nRkxSIQvnRHuMnuIn9tc4jlbDZdGZdK/lJMNJVXV2+Xaqno8cVkxcaek+m/DVlzGSzEewBSiFgXsmW2ci3Aq2sVLrI//8AABISBkgeCwVqO/rfaiLACdcukxqUc7H6pb+J1L77u1wnqOWwUEuF0MD29Saer77Y/LU8+ehrcnFK+UEmvdLb/OoeqXT4UVFQnZB6stAuuUq57+yia7838fb6Hi7uwZFxdO/mlijjbQuq/QBDciAfJz9AiKjh/gq5SMReVSCNfwl7NLGy3b/Wv+KuSVsjdMS9ICnBYE2UMLj0PCTRGkZB8Fo4= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > Hugetlb reservations are accounted globally, but hugetlb_acct_memory() > also verifies that the current cpuset and MPOL_BIND policy contain enou= gh > free huge pages to add a new reservation. >=20 >=20gather_surplus_pages() calculates its allocation shortfall from the g= lobal > free and reserved counters. If the global pool has enough free pages, b= ut > those pages reside outside the nodes allowed by the task, it allocates = no > surplus pages. The subsequent allowed_mems_nr() check then rejects the > reservation and mmap() fails with ENOMEM, even when > nr_overcommit_hugepages permits allocating surplus pages on the allowed > nodes. >=20 >=20Calculate both the global shortfall and the shortfall within the allo= wed > nodes, and allocate the larger of the two. Include surplus pages alloca= ted > outside hugetlb_lock in both calculations when rechecking after reacqui= ring > the lock. These pages are constrained by alloc_nodemask, so they satisf= y > both shortages. >=20 >=20Easy way to reproduce this issue with 2+ NUMA nodes system: >=20 >=20 # echo 0 > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepage > # echo 3 > /sys/devices/system/node/node0/hugepages/hugepages-2048kB/n= r_hugepages > # echo 1 > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_overcommit_hug= epages > # cd tools/testing/selftests/mm > # numactl --membind=3D1 ./hugetlb-mmap 2 21 > TAP version 13 > # [INFO] detected hugetlb page size: 2048 KiB > # [INFO] detected hugetlb page size: 1048576 KiB > # 2048 kB hugepages > 1..2 > # Mapping 2 Mbytes > Bail out! mmap: Cannot allocate memory (12) > # Planned tests !=3D run tests (2 !=3D 0) > # Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0 >=20 >=20This fixes hugetlb mappings when, for example, a task runs with > MPOL_BIND on Node 1 while the existing free huge pages are on Node 0. >=20 >=20Similar issue also could be found in ltp if the free pages of global = pool > reside outside the nodes allowed by the application. > # cd ltp/testcases/kernel/mem/hugetlb/hugemmap/ > # numactl --cpunodebind=3D0 --membind=3D1 ./hugemmap10 >=20 >=20Signed-off-by: Huaisheng Ye Tested-by: Li Wang Regards, Li Wang