| From: Luiz Capitulino <luizcap@redhat.com> |
| Subject: mm: hugetlb: avoid fallback for specific node allocation of 1G pages |
| Date: Mon, 10 Feb 2025 22:48:56 -0500 |
| |
| When using the HugeTLB kernel command-line to allocate 1G pages from a |
| specific node, such as: |
| |
| default_hugepagesz=1G hugepages=1:1 |
| |
| If node 1 happens to not have enough memory for the requested number of 1G |
| pages, the allocation falls back to other nodes. A quick way to reproduce |
| this is by creating a KVM guest with a memory-less node and trying to |
| allocate 1 1G page from it. Instead of failing, the allocation will |
| fallback to other nodes. |
| |
| This defeats the purpose of node specific allocation. Also, specific node |
| allocation for 2M pages don't have this behavior: the allocation will just |
| fail for the pages it can't satisfy. |
| |
| This issue happens because HugeTLB calls memblock_alloc_try_nid_raw() for |
| 1G boot-time allocation as this function falls back to other nodes if the |
| allocation can't be satisfied. Use memblock_alloc_exact_nid_raw() |
| instead, which ensures that the allocation will only be satisfied from the |
| specified node. |
| |
| Link: https://lkml.kernel.org/r/20250211034856.629371-1-luizcap@redhat.com |
| Fixes: b5389086ad7b ("hugetlbfs: extend the definition of hugepages parameter to support node allocation") |
| Signed-off-by: Luiz Capitulino <luizcap@redhat.com> |
| Acked-by: Oscar Salvador <osalvador@suse.de> |
| Acked-by: David Hildenbrand <david@redhat.com> |
| Cc: "Mike Rapoport (IBM)" <rppt@kernel.org> |
| Cc: Muchun Song <muchun.song@linux.dev> |
| Cc: Zhenguo Yao <yaozhenguo1@gmail.com> |
| Cc: Frank van der Linden <fvdl@google.com> |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| --- |
| |
| mm/hugetlb.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| --- a/mm/hugetlb.c~mm-hugetlb-avoid-fallback-for-specific-node-allocation-of-1g-pages |
| +++ a/mm/hugetlb.c |
| @@ -3145,7 +3145,7 @@ int __alloc_bootmem_huge_page(struct hst |
| |
| /* do node specific alloc */ |
| if (nid != NUMA_NO_NODE) { |
| - m = memblock_alloc_try_nid_raw(huge_page_size(h), huge_page_size(h), |
| + m = memblock_alloc_exact_nid_raw(huge_page_size(h), huge_page_size(h), |
| 0, MEMBLOCK_ALLOC_ACCESSIBLE, nid); |
| if (!m) |
| return 0; |
| _ |
