+ mm-hugetlb_cma-support-percentage-based-hugetlb_cma-reservation.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/hugetlb_cma: support percentage-based hugetlb_cma reservation
has been added to the -mm mm-new branch.  Its filename is
     mm-hugetlb_cma-support-percentage-based-hugetlb_cma-reservation.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-hugetlb_cma-support-percentage-based-hugetlb_cma-reservation.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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------------------------------------------------------
From: Sourav Panda <souravpanda@google.com>
Subject: mm/hugetlb_cma: support percentage-based hugetlb_cma reservation
Date: Sun, 28 Jun 2026 19:01:55 +0000

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/20260628190155.3655895-1-souravpanda@google.com
Signed-off-by: Sourav Panda <souravpanda@google.com>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202606262023.IKUrn01I-lkp@intel.com/
Cc: David Hildenbrand <david@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Frank van der Linden <fvdl@google.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 Documentation/admin-guide/kernel-parameters.txt |    7 -
 mm/hugetlb_cma.c                                |   96 +++++++++++++-
 2 files changed, 97 insertions(+), 6 deletions(-)

--- a/Documentation/admin-guide/kernel-parameters.txt~mm-hugetlb_cma-support-percentage-based-hugetlb_cma-reservation
+++ a/Documentation/admin-guide/kernel-parameters.txt
@@ -2064,8 +2064,11 @@ 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)
-				<node>:nn[KMGTPE][,<node>: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%).
+			Format: nn[KMGTPE] or nn% or (node format)
+				<node>:nn[KMGTPE][,<node>:nn[KMGTPE]] or
+				<node>:nn%[,<node>:nn%]
 
 			The size must be a multiple of the gigantic page size.
 			When using node format, this applies to each per-node size.
--- a/mm/hugetlb_cma.c~mm-hugetlb_cma-support-percentage-based-hugetlb_cma-reservation
+++ a/mm/hugetlb_cma.c
@@ -9,6 +9,9 @@
 #include <asm/setup.h>
 
 #include <linux/hugetlb.h>
+#include <linux/memblock.h>
+#include <linux/math.h>
+#include <linux/math64.h>
 #include "internal.h"
 #include "hugetlb_cma.h"
 
@@ -18,6 +21,28 @@ static unsigned long hugetlb_cma_size_in
 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 +115,28 @@ static int __init cmdline_parse_hugetlb_
 			break;
 
 		if (s[count] == ':') {
+			char *next;
+
 			if (tmp >= MAX_NUMNODES)
 				break;
 			nid = array_index_nospec(tmp, MAX_NUMNODES);
 
 			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 +147,28 @@ static int __init cmdline_parse_hugetlb_
 			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 +194,36 @@ 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;
 
_

Patches currently in -mm which might be from souravpanda@google.com are

mm-hugetlb_cma-support-percentage-based-hugetlb_cma-reservation.patch