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Commit 39fa104d authored by Reza Arbab's avatar Reza Arbab Committed by Linus Torvalds
Browse files

mm: remove x86-only restriction of movable_node 

In commit c5320926 ("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.

Link: http://lkml.kernel.org/r/1479160961-25840-3-git-send-email-arbab@linux.vnet.ibm.com


Signed-off-by: default avatarReza Arbab <arbab@linux.vnet.ibm.com>
Acked-by: default avatarBalbir Singh <bsingharora@gmail.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Alistair Popple <apopple@au1.ibm.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Bharata B Rao <bharata@linux.vnet.ibm.com>
Cc: Frank Rowand <frowand.list@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Stewart Smith <stewart@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4a3bac4e

Documentation/kernel-parameters.txt

+1 −1
Original line number Diff line number Diff line
@@ -2406,7 +2406,7 @@ 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]

arch/x86/kernel/setup.c

+24 −0
Original line number Diff line number Diff line
@@ -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 */

mm/memory_hotplug.c

+0 −20
Original line number Diff line number Diff line
@@ -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");