@@ -1892,6 +1892,13 @@
hugepages using the CMA allocator. If enabled, the
boot-time allocation of gigantic hugepages is skipped.
+ hugetlb_cma_only=
+ [HW,CMA,EARLY] When allocating new HugeTLB pages, only
+ try to allocate from the CMA areas.
+
+ This option does nothing if hugetlb_cma= is not also
+ specified.
+
hugetlb_free_vmemmap=
[KNL] Requires CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
enabled.
@@ -60,6 +60,7 @@ struct hstate hstates[HUGE_MAX_HSTATE];
static struct cma *hugetlb_cma[MAX_NUMNODES];
static unsigned long hugetlb_cma_size_in_node[MAX_NUMNODES] __initdata;
#endif
+static bool hugetlb_cma_only;
static unsigned long hugetlb_cma_size __initdata;
__initdata struct list_head huge_boot_pages[MAX_NUMNODES];
@@ -1511,6 +1512,9 @@ static struct folio *alloc_gigantic_folio(struct hstate *h, gfp_t gfp_mask,
}
#endif
if (!folio) {
+ if (hugetlb_cma_only)
+ return NULL;
+
folio = folio_alloc_gigantic(order, gfp_mask, nid, nodemask);
if (!folio)
return NULL;
@@ -4732,6 +4736,9 @@ static __init void hugetlb_parse_params(void)
hcp->setup(hcp->val);
}
+
+ if (!hugetlb_cma_size)
+ hugetlb_cma_only = false;
}
/*
@@ -7844,6 +7851,13 @@ static int __init cmdline_parse_hugetlb_cma(char *p)
early_param("hugetlb_cma", cmdline_parse_hugetlb_cma);
+static int __init cmdline_parse_hugetlb_cma_only(char *p)
+{
+ return kstrtobool(p, &hugetlb_cma_only);
+}
+
+early_param("hugetlb_cma_only", cmdline_parse_hugetlb_cma_only);
+
void __init hugetlb_cma_reserve(int order)
{
unsigned long size, reserved, per_node;
Add an option to force hugetlb gigantic pages to be allocated using CMA only (if hugetlb_cma is enabled). This avoids a fallback to allocation from the rest of system memory if the CMA allocation fails. This makes the size of hugetlb_cma a hard upper boundary for gigantic hugetlb page allocations. This is useful because, with a large CMA area, the kernel's unmovable allocations will have less room to work with and it is undesirable for new hugetlb gigantic page allocations to be done from that remaining area. It will eat in to the space available for unmovable allocations, leading to unwanted system behavior (OOMs because the kernel fails to do unmovable allocations). So, with this enabled, an administrator can force a hard upper bound for runtime gigantic page allocations, and have more predictable system behavior. Signed-off-by: Frank van der Linden <fvdl@google.com> --- Documentation/admin-guide/kernel-parameters.txt | 7 +++++++ mm/hugetlb.c | 14 ++++++++++++++ 2 files changed, 21 insertions(+)