This is a common condition used to skip operations that cannot be performed on gigantic pages when runtime support is disabled. This helper is introduced as the condition will exist even more when allowing "overcommit" of gigantic hugepages. No functional change intended with this patch. Suggested-by: Andrew Morton Signed-off-by: Usama Arif --- mm/hugetlb.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index c07b7192aff26..e74e41386b100 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -134,6 +134,17 @@ static void hugetlb_free_folio(struct folio *folio) folio_put(folio); } +/* + * Check if the hstate represents gigantic pages but gigantic page + * runtime support is not available. This is a common condition used to + * skip operations that cannot be performed on gigantic pages when runtime + * support is disabled. + */ +static inline bool hstate_is_gigantic_no_runtime(struct hstate *h) +{ + return hstate_is_gigantic(h) && !gigantic_page_runtime_supported(); +} + static inline bool subpool_is_free(struct hugepage_subpool *spool) { if (spool->count) @@ -1555,7 +1566,7 @@ static void remove_hugetlb_folio(struct hstate *h, struct folio *folio, VM_BUG_ON_FOLIO(hugetlb_cgroup_from_folio_rsvd(folio), folio); lockdep_assert_held(&hugetlb_lock); - if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported()) + if (hstate_is_gigantic_no_runtime(h)) return; list_del(&folio->lru); @@ -1617,7 +1628,7 @@ static void __update_and_free_hugetlb_folio(struct hstate *h, { bool clear_flag = folio_test_hugetlb_vmemmap_optimized(folio); - if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported()) + if (hstate_is_gigantic_no_runtime(h)) return; /* @@ -2511,7 +2522,7 @@ static void return_unused_surplus_pages(struct hstate *h, /* Uncommit the reservation */ h->resv_huge_pages -= unused_resv_pages; - if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported()) + if (hstate_is_gigantic_no_runtime(h)) goto out; /* @@ -3725,7 +3736,7 @@ static void __init hugetlb_init_hstates(void) * - If CMA allocation is possible, we can not demote * HUGETLB_PAGE_ORDER or smaller size pages. */ - if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported()) + if (hstate_is_gigantic_no_runtime(h)) continue; if (hugetlb_cma_total_size() && h->order <= HUGETLB_PAGE_ORDER) continue; @@ -4202,7 +4213,7 @@ static ssize_t __nr_hugepages_store_common(bool obey_mempolicy, int err; nodemask_t nodes_allowed, *n_mask; - if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported()) + if (hstate_is_gigantic_no_runtime(h)) return -EINVAL; if (nid == NUMA_NO_NODE) { -- 2.47.3 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. The restriction was added in 2011 [1], which was before there was support for reserving 1G hugepages at runtime. 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); ... [1] https://git.zx2c4.com/linux-rng/commit/mm/hugetlb.c?id=adbe8726dc2a3805630d517270db17e3af86e526 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 e74e41386b100..c0036c0775d75 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -2243,7 +2243,7 @@ static struct folio *alloc_surplus_hugetlb_folio(struct hstate *h, { struct folio *folio = NULL; - if (hstate_is_gigantic(h)) + if (hstate_is_gigantic_no_runtime(h)) return NULL; spin_lock_irq(&hugetlb_lock); @@ -4305,7 +4305,7 @@ 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_no_runtime(h)) return -EINVAL; err = kstrtoul(buf, 10, &input); @@ -5192,7 +5192,7 @@ 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_no_runtime(h)) return -EINVAL; ret = proc_hugetlb_doulongvec_minmax(table, write, buffer, length, ppos, -- 2.47.3