In commit c5320926e370 ("mem-hotplug: introduce movable_node boot
option"), the memblock allocation direction is changed to bottom-up and
then back to top-down like this:
1. memblock_set_bottom_up(true), called by cmdline_parse_movable_node().
2. memblock_set_bottom_up(false), called by x86's numa_init().
Even though (1) occurs in generic mm code, it is wrapped by #ifdef
CONFIG_MOVABLE_NODE, which depends on X86_64.
This means that when we extend CONFIG_MOVABLE_NODE to non-x86 arches,
things will be unbalanced. (1) will happen for them, but (2) will not.
This toggle was added in the first place because x86 has a delay between
adding memblocks and marking them as hotpluggable. Since other arches do
this marking either immediately or not at all, they do not require the
bottom-up toggle.
So, resolve things by moving (1) from cmdline_parse_movable_node() to
x86's setup_arch(), immediately after the movable_node parameter has
been parsed.
Signed-off-by: Reza Arbab <arbab@xxxxxxxxxxxxxxxxxx>
---
Documentation/kernel-parameters.txt | 2 +-
arch/x86/kernel/setup.c | 24 ++++++++++++++++++++++++
mm/memory_hotplug.c | 20 --------------------
3 files changed, 25 insertions(+), 21 deletions(-)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 37babf9..adcccd5 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2401,7 +2401,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
that the amount of memory usable for all allocations
is not too small.
- movable_node [KNL,X86] Boot-time switch to enable the effects
+ movable_node [KNL] Boot-time switch to enable the effects
of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
MTD_Partition= [MTD]
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 9c337b0..4cfba94 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -985,6 +985,30 @@ void __init setup_arch(char **cmdline_p)
parse_early_param();
+#ifdef CONFIG_MEMORY_HOTPLUG
+ /*
+ * Memory used by the kernel cannot be hot-removed because Linux
+ * cannot migrate the kernel pages. When memory hotplug is
+ * enabled, we should prevent memblock from allocating memory
+ * for the kernel.
+ *
+ * ACPI SRAT records all hotpluggable memory ranges. But before
+ * SRAT is parsed, we don't know about it.
+ *
+ * The kernel image is loaded into memory at very early time. We
+ * cannot prevent this anyway. So on NUMA system, we set any
+ * node the kernel resides in as un-hotpluggable.
+ *
+ * Since on modern servers, one node could have double-digit
+ * gigabytes memory, we can assume the memory around the kernel
+ * image is also un-hotpluggable. So before SRAT is parsed, just
+ * allocate memory near the kernel image to try the best to keep
+ * the kernel away from hotpluggable memory.
+ */
+ if (movable_node_is_enabled())
+ memblock_set_bottom_up(true);
+#endif
+
x86_report_nx();
/* after early param, so could get panic from serial */
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index cad4b91..e43142c1 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1727,26 +1727,6 @@ static bool can_offline_normal(struct zone *zone, unsigned long nr_pages)
static int __init cmdline_parse_movable_node(char *p)
{
#ifdef CONFIG_MOVABLE_NODE
- /*
- * Memory used by the kernel cannot be hot-removed because Linux
- * cannot migrate the kernel pages. When memory hotplug is
- * enabled, we should prevent memblock from allocating memory
- * for the kernel.
- *
- * ACPI SRAT records all hotpluggable memory ranges. But before
- * SRAT is parsed, we don't know about it.
- *
- * The kernel image is loaded into memory at very early time. We
- * cannot prevent this anyway. So on NUMA system, we set any
- * node the kernel resides in as un-hotpluggable.
- *
- * Since on modern servers, one node could have double-digit
- * gigabytes memory, we can assume the memory around the kernel
- * image is also un-hotpluggable. So before SRAT is parsed, just
- * allocate memory near the kernel image to try the best to keep
- * the kernel away from hotpluggable memory.
- */
- memblock_set_bottom_up(true);
movable_node_enabled = true;
#else
pr_warn("movable_node option not supported\n");
--
1.8.3.1
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