Currently, gigantic hugepages cannot use the overcommit mechanism (nr_overcommit_hugepages), forcing users to permanently reserve memory via nr_hugepages even when pages might not be actively used. Remove this blanket restriction on gigantic hugepage overcommit. This will bring the same benefits to gigantic pages as hugepages: - Memory is only taken out of regular use when actually needed - Unused surplus pages can be returned to the system - Better memory utilization, especially with CMA backing which can significantly increase the changes of hugepage allocation Without this patch: echo 3 > /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_overcommit_hugepages bash: echo: write error: Invalid argument With this patch: echo 3 > /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_overcommit_hugepages ./mmap_hugetlb_test Successfully allocated huge pages at address: 0x7f9d40000000 cat mmap_hugetlb_test.c ... unsigned long ALLOC_SIZE = 3 * (unsigned long) HUGE_PAGE_SIZE; addr = mmap(NULL, ALLOC_SIZE, // 3GB PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB | MAP_HUGE_1GB, -1, 0); if (addr == MAP_FAILED) { fprintf(stderr, "mmap failed: %s\n", strerror(errno)); return 1; } printf("Successfully allocated huge pages at address: %p\n", addr); ... Signed-off-by: Usama Arif --- mm/hugetlb.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index c07b7192aff26..93d0f8ae1fe84 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -2232,7 +2232,7 @@ static struct folio *alloc_surplus_hugetlb_folio(struct hstate *h, { struct folio *folio = NULL; - if (hstate_is_gigantic(h)) + if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported()) return NULL; spin_lock_irq(&hugetlb_lock); @@ -4294,7 +4294,7 @@ static ssize_t nr_overcommit_hugepages_store(struct kobject *kobj, unsigned long input; struct hstate *h = kobj_to_hstate(kobj, NULL); - if (hstate_is_gigantic(h)) + if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported()) return -EINVAL; err = kstrtoul(buf, 10, &input); @@ -5181,7 +5181,7 @@ static int hugetlb_overcommit_handler(const struct ctl_table *table, int write, tmp = h->nr_overcommit_huge_pages; - if (write && hstate_is_gigantic(h)) + if (write && hstate_is_gigantic(h) && !gigantic_page_runtime_supported()) return -EINVAL; ret = proc_hugetlb_doulongvec_minmax(table, write, buffer, length, ppos, -- 2.47.3