From: yangge yangge1116@126.com
My machine has 4 NUMA nodes, each equipped with 32GB of memory. I have configured each NUMA node with 16GB of CMA and 16GB of in-use hugetlb pages. The allocation of contiguous memory via the cma_alloc() function can fail probabilistically.
The cma_alloc() function may fail if it sees an in-use hugetlb page within the allocation range, even if that page has already been migrated. When in-use hugetlb pages are migrated, they may simply be released back into the free hugepage pool instead of being returned to the buddy system. This can cause the test_pages_isolated() function check to fail, ultimately leading to the failure of the cma_alloc() function: cma_alloc() __alloc_contig_migrate_range() // migrate in-use hugepage test_pages_isolated() __test_page_isolated_in_pageblock() PageBuddy(page) // check if the page is in buddy
To address this issue, we will add a function named replace_free_hugepage_folios(). This function will replace the hugepage in the free hugepage pool with a new one and release the old one to the buddy system. After the migration of in-use hugetlb pages is completed, we will invoke the replace_free_hugepage_folios() function to ensure that these hugepages are properly released to the buddy system. Following this step, when the test_pages_isolated() function is executed for inspection, it will successfully pass.
Signed-off-by: yangge yangge1116@126.com --- include/linux/hugetlb.h | 6 ++++++ mm/hugetlb.c | 37 +++++++++++++++++++++++++++++++++++++ mm/page_alloc.c | 13 ++++++++++++- 3 files changed, 55 insertions(+), 1 deletion(-)
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index ae4fe86..7d36ac8 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -681,6 +681,7 @@ struct huge_bootmem_page { };
int isolate_or_dissolve_huge_page(struct page *page, struct list_head *list); +int replace_free_hugepage_folios(unsigned long start_pfn, unsigned long end_pfn); struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma, unsigned long addr, int avoid_reserve); struct folio *alloc_hugetlb_folio_nodemask(struct hstate *h, int preferred_nid, @@ -1059,6 +1060,11 @@ static inline int isolate_or_dissolve_huge_page(struct page *page, return -ENOMEM; }
+int replace_free_hugepage_folios(unsigned long start_pfn, unsigned long end_pfn) +{ + return 0; +} + static inline struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma, unsigned long addr, int avoid_reserve) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 8e1db80..a099c54 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -2975,6 +2975,43 @@ int isolate_or_dissolve_huge_page(struct page *page, struct list_head *list) return ret; }
+/* + * replace_free_hugepage_folios - Replace free hugepage folios in a given pfn + * range with new folios. + * @stat_pfn: start pfn of the given pfn range + * @end_pfn: end pfn of the given pfn range + * Returns 0 on success, otherwise negated error. + */ +int replace_free_hugepage_folios(unsigned long start_pfn, unsigned long end_pfn) +{ + struct hstate *h; + struct folio *folio; + int ret = 0; + + LIST_HEAD(isolate_list); + + while (start_pfn < end_pfn) { + folio = pfn_folio(start_pfn); + if (folio_test_hugetlb(folio)) { + h = folio_hstate(folio); + } else { + start_pfn++; + continue; + } + + if (!folio_ref_count(folio)) { + ret = alloc_and_dissolve_hugetlb_folio(h, folio, &isolate_list); + if (ret) + break; + + putback_movable_pages(&isolate_list); + } + start_pfn++; + } + + return ret; +} + struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma, unsigned long addr, int avoid_reserve) { diff --git a/mm/page_alloc.c b/mm/page_alloc.c index dde19db..1dcea28 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -6504,7 +6504,18 @@ int alloc_contig_range_noprof(unsigned long start, unsigned long end, ret = __alloc_contig_migrate_range(&cc, start, end, migratetype); if (ret && ret != -EBUSY) goto done; - ret = 0; + + /* + * When in-use hugetlb pages are migrated, they may simply be + * released back into the free hugepage pool instead of being + * returned to the buddy system. After the migration of in-use + * huge pages is completed, we will invoke the + * replace_free_hugepage_folios() function to ensure that + * these hugepages are properly released to the buddy system. + */ + ret = replace_free_hugepage_folios(start, end); + if (ret) + goto done;
/* * Pages from [start, end) are within a pageblock_nr_pages