diff options
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/Kconfig | 17 | ||||
| -rw-r--r-- | mm/memory_hotplug.c | 31 |
2 files changed, 43 insertions, 5 deletions
diff --git a/mm/Kconfig b/mm/Kconfig index 394838f489eb..3f4ffda152bb 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -153,11 +153,18 @@ config MOVABLE_NODE help Allow a node to have only movable memory. Pages used by the kernel, such as direct mapping pages cannot be migrated. So the corresponding - memory device cannot be hotplugged. This option allows users to - online all the memory of a node as movable memory so that the whole - node can be hotplugged. Users who don't use the memory hotplug - feature are fine with this option on since they don't online memory - as movable. + memory device cannot be hotplugged. This option allows the following + two things: + - When the system is booting, node full of hotpluggable memory can + be arranged to have only movable memory so that the whole node can + be hot-removed. (need movable_node boot option specified). + - After the system is up, the option allows users to online all the + memory of a node as movable memory so that the whole node can be + hot-removed. + + Users who don't use the memory hotplug feature are fine with this + option on since they don't specify movable_node boot option or they + don't online memory as movable. Say Y here if you want to hotplug a whole node. Say N here if you want kernel to use memory on all nodes evenly. diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 1b6fe8ca71e6..489f235502db 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -31,6 +31,7 @@ #include <linux/firmware-map.h> #include <linux/stop_machine.h> #include <linux/hugetlb.h> +#include <linux/memblock.h> #include <asm/tlbflush.h> @@ -1422,6 +1423,36 @@ static bool can_offline_normal(struct zone *zone, unsigned long nr_pages) } #endif /* CONFIG_MOVABLE_NODE */ +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); +#else + pr_warn("movable_node option not supported\n"); +#endif + return 0; +} +early_param("movable_node", cmdline_parse_movable_node); + /* check which state of node_states will be changed when offline memory */ static void node_states_check_changes_offline(unsigned long nr_pages, struct zone *zone, struct memory_notify *arg) |