From 34e0849142c317eed68f3a4818dd3808fb1c47db Mon Sep 17 00:00:00 2001 From: Sourav Panda Date: Fri, 7 Aug 2026 04:00:03 +0000 Subject: [PATCH] mm/hugetlb_cma: support percentage-based hugetlb_cma reservation Currently, hugetlb_cma reservation only supports absolute sizes (e.g., hugetlb_cma=2G or hugetlb_cma=0:1G,1:1G). This can be restrictive in heterogeneous environments or when deploying common kernel command lines across machines with different memory capacities. Add support for percentage-based hugetlb_cma reservation (e.g., hugetlb_cma=20% or hugetlb_cma=0:20%,1:10%). The percentage is calculated against the total memory (for global settings) or against the node-specific memory (for node-specific settings) using memblock APIs during early boot. Link: https://lore.kernel.org/20260807040003.2156630-1-souravpanda@google.com Signed-off-by: Sourav Panda Acked-by: Usama Arif Cc: David Hildenbrand Cc: David Rientjes Cc: Frank van der Linden Cc: Greg Thelen Cc: Muchun Song Cc: Oscar Salvador Cc: Suren Baghdasaryan Signed-off-by: Andrew Morton --- .../admin-guide/kernel-parameters.txt | 10 +- mm/hugetlb_cma.c | 142 +++++++++++++++++- 2 files changed, 142 insertions(+), 10 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 364c2dce8e70..1af62cd16c9d 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2064,8 +2064,14 @@ Kernel parameters hugetlb_cma= [HW,CMA,EARLY] The size of a CMA area used for allocation of gigantic hugepages. Or using node format, the size of a CMA area per node can be specified. - Format: nn[KMGTPE] or (node format) - :nn[KMGTPE][,:nn[KMGTPE]] + The size can be an absolute value (e.g., 2G) or a + percentage of the total memory or node memory (e.g., 20%). + Percentage-derived sizes are rounded down to a multiple of + the architecture's gigantic hugepage size and may become + zero. + Format: nn[KMGTPE] or nn% or (node format) + :nn[KMGTPE][,:nn[KMGTPE]] or + :nn%[,:nn%] The size must be a multiple of the gigantic page size. When using node format, this applies to each per-node size. diff --git a/mm/hugetlb_cma.c b/mm/hugetlb_cma.c index 4dfce68b354a..db0680e82847 100644 --- a/mm/hugetlb_cma.c +++ b/mm/hugetlb_cma.c @@ -9,6 +9,9 @@ #include #include +#include +#include +#include #include "internal.h" #include "hugetlb_cma.h" @@ -18,6 +21,28 @@ static unsigned long hugetlb_cma_size_in_node[MAX_NUMNODES] __initdata; static bool hugetlb_cma_only __ro_after_init; static unsigned long hugetlb_cma_size __ro_after_init; +static unsigned int hugetlb_cma_percent __initdata; +static unsigned int hugetlb_cma_percent_in_node[MAX_NUMNODES] __initdata; + +#ifdef CONFIG_NUMA +static phys_addr_t __init memblock_node_memory_size(int nid) +{ + struct memblock_region *reg; + phys_addr_t size = 0; + + for_each_mem_region(reg) { + if (reg->nid == nid) + size += reg->size; + } + return size; +} +#else +static phys_addr_t __init memblock_node_memory_size(int nid) +{ + return memblock_phys_mem_size(); +} +#endif + void hugetlb_cma_free_frozen_folio(struct folio *folio) { WARN_ON_ONCE(!cma_release_frozen(hugetlb_cma[folio_nid(folio)], @@ -90,14 +115,31 @@ static int __init cmdline_parse_hugetlb_cma(char *p) break; if (s[count] == ':') { + char *next; + if (tmp >= MAX_NUMNODES) break; nid = array_index_nospec(tmp, MAX_NUMNODES); + hugetlb_cma_size = 0; + hugetlb_cma_percent = 0; + s += count + 1; - tmp = memparse(s, &s); - hugetlb_cma_size_in_node[nid] = tmp; - hugetlb_cma_size += tmp; + tmp = memparse(s, &next); + if (*next == '%') { + if (tmp > 100) { + pr_warn("hugetlb_cma: invalid percentage %lu for node %d\n", + tmp, nid); + break; + } + hugetlb_cma_percent_in_node[nid] = tmp; + hugetlb_cma_size_in_node[nid] = 0; + s = next + 1; + } else { + hugetlb_cma_size_in_node[nid] = tmp; + hugetlb_cma_percent_in_node[nid] = 0; + s = next; + } /* * Skip the separator if have one, otherwise @@ -108,7 +150,28 @@ static int __init cmdline_parse_hugetlb_cma(char *p) else break; } else { - hugetlb_cma_size = memparse(p, &p); + char *next; + + tmp = memparse(p, &next); + if (*next == '%') { + if (tmp > 100) { + pr_warn("hugetlb_cma: invalid percentage %lu\n", tmp); + } else { + hugetlb_cma_percent = tmp; + hugetlb_cma_size = 0; + for (nid = 0; nid < MAX_NUMNODES; nid++) { + hugetlb_cma_size_in_node[nid] = 0; + hugetlb_cma_percent_in_node[nid] = 0; + } + } + } else { + hugetlb_cma_size = tmp; + hugetlb_cma_percent = 0; + for (nid = 0; nid < MAX_NUMNODES; nid++) { + hugetlb_cma_size_in_node[nid] = 0; + hugetlb_cma_percent_in_node[nid] = 0; + } + } break; } } @@ -134,8 +197,36 @@ void __init hugetlb_cma_reserve(void) { unsigned long size, reserved, per_node, order, gigantic_page_size; bool node_specific_cma_alloc = false; + bool has_node_specific_param = false; int nid; + for (nid = 0; nid < MAX_NUMNODES; nid++) { + if (hugetlb_cma_size_in_node[nid] || hugetlb_cma_percent_in_node[nid]) { + has_node_specific_param = true; + break; + } + } + + if (has_node_specific_param) { + hugetlb_cma_size = 0; + for (nid = 0; nid < MAX_NUMNODES; nid++) { + if (hugetlb_cma_percent_in_node[nid]) { + phys_addr_t node_gfp_mem = memblock_node_memory_size(nid); + u64 s; + + s = mul_u64_u32_div((u64)node_gfp_mem, + hugetlb_cma_percent_in_node[nid], + 100); + + hugetlb_cma_size_in_node[nid] = s; + } + hugetlb_cma_size += hugetlb_cma_size_in_node[nid]; + } + } else if (hugetlb_cma_percent) { + hugetlb_cma_size = mul_u64_u32_div((u64)memblock_phys_mem_size(), + hugetlb_cma_percent, 100); + } + if (!hugetlb_cma_size) return; @@ -154,6 +245,32 @@ void __init hugetlb_cma_reserve(void) VM_WARN_ON(order <= MAX_PAGE_ORDER); gigantic_page_size = PAGE_SIZE << order; + if (hugetlb_cma_percent) { + unsigned long orig_size = hugetlb_cma_size; + + hugetlb_cma_size = ALIGN_DOWN(hugetlb_cma_size, PAGE_SIZE << order); + if (orig_size && !hugetlb_cma_size) + pr_warn("hugetlb_cma: reservation size rounded down to 0 from %lu MiB (%u%%)\n", + orig_size / SZ_1M, hugetlb_cma_percent); + } else if (has_node_specific_param) { + hugetlb_cma_size = 0; + for (nid = 0; nid < MAX_NUMNODES; nid++) { + if (hugetlb_cma_percent_in_node[nid]) { + unsigned long orig_size = hugetlb_cma_size_in_node[nid]; + + hugetlb_cma_size_in_node[nid] = + ALIGN_DOWN(hugetlb_cma_size_in_node[nid], + PAGE_SIZE << order); + if (orig_size && !hugetlb_cma_size_in_node[nid]) + pr_warn("hugetlb_cma: reservation size rounded down to 0 from %lu MiB (%u%%) on node %d\n", + orig_size / SZ_1M, + hugetlb_cma_percent_in_node[nid], + nid); + } + hugetlb_cma_size += hugetlb_cma_size_in_node[nid]; + } + } + hugetlb_bootmem_set_nodes(); for (nid = 0; nid < MAX_NUMNODES; nid++) { @@ -194,8 +311,13 @@ void __init hugetlb_cma_reserve(void) per_node = DIV_ROUND_UP(hugetlb_cma_size, nodes_weight(hugetlb_bootmem_nodes)); per_node = round_up(per_node, gigantic_page_size); - pr_info("hugetlb_cma: reserve %lu MiB, up to %lu MiB per node\n", - hugetlb_cma_size / SZ_1M, per_node / SZ_1M); + if (hugetlb_cma_percent) + pr_info("hugetlb_cma: reserve %lu MiB (%u%%), up to %lu MiB per node\n", + hugetlb_cma_size / SZ_1M, hugetlb_cma_percent, + per_node / SZ_1M); + else + pr_info("hugetlb_cma: reserve %lu MiB, up to %lu MiB per node\n", + hugetlb_cma_size / SZ_1M, per_node / SZ_1M); } reserved = 0; @@ -230,8 +352,12 @@ void __init hugetlb_cma_reserve(void) } reserved += size; - pr_info("hugetlb_cma: reserved %lu MiB on node %d\n", - size / SZ_1M, nid); + if (hugetlb_cma_percent_in_node[nid]) + pr_info("hugetlb_cma: reserved %lu MiB (%u%%) on node %d\n", + size / SZ_1M, hugetlb_cma_percent_in_node[nid], nid); + else + pr_info("hugetlb_cma: reserved %lu MiB on node %d\n", + size / SZ_1M, nid); if (reserved >= hugetlb_cma_size) break;