Commit 23baf831 authored by Kirill A. Shutemov's avatar Kirill A. Shutemov Committed by Andrew Morton
Browse files

mm, treewide: redefine MAX_ORDER sanely 

MAX_ORDER currently defined as number of orders page allocator supports:
user can ask buddy allocator for page order between 0 and MAX_ORDER-1.

This definition is counter-intuitive and lead to number of bugs all over
the kernel.

Change the definition of MAX_ORDER to be inclusive: the range of orders
user can ask from buddy allocator is 0..MAX_ORDER now.

[kirill@shutemov.name: fix min() warning]
  Link: https://lkml.kernel.org/r/20230315153800.32wib3n5rickolvh@box
[akpm@linux-foundation.org: fix another min_t warning]
[kirill@shutemov.name: fixups per Zi Yan]
  Link: https://lkml.kernel.org/r/20230316232144.b7ic4cif4kjiabws@box.shutemov.name
[akpm@linux-foundation.org: fix underlining in docs]
  Link: https://lore.kernel.org/oe-kbuild-all/202303191025.VRCTk6mP-lkp@intel.com/
Link: https://lkml.kernel.org/r/20230315113133.11326-11-kirill.shutemov@linux.intel.com


Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Michael Ellerman <mpe@ellerman.id.au>	[powerpc]
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 61883d3c

Documentation/admin-guide/kdump/vmcoreinfo.rst

+3 −3
Original line number Diff line number Diff line
@@ -172,7 +172,7 @@ variables. 
Offset of the free_list's member. This value is used to compute the number

of free pages.



Each zone has a free_area structure array called free_area[MAX_ORDER].

Each zone has a free_area structure array called free_area[MAX_ORDER + 1].

The free_list represents a linked list of free page blocks.



(list_head, next|prev)
@@ -189,8 +189,8 @@ Offsets of the vmap_area's members. They carry vmalloc-specific 
information. Makedumpfile gets the start address of the vmalloc region

from this.



(zone.free_area, MAX_ORDER)

---------------------------

(zone.free_area, MAX_ORDER + 1)

-------------------------------



Free areas descriptor. User-space tools use this value to iterate the

free_area ranges. MAX_ORDER is used by the zone buddy allocator.

Documentation/admin-guide/kernel-parameters.txt

+1 −1
Original line number Diff line number Diff line
@@ -3969,7 +3969,7 @@ 
			[KNL] Minimal page reporting order

			Format: <integer>

			Adjust the minimal page reporting order. The page

			reporting is disabled when it exceeds (MAX_ORDER-1).

			reporting is disabled when it exceeds MAX_ORDER.



	panic=		[KNL] Kernel behaviour on panic: delay <timeout>

			timeout > 0: seconds before rebooting

arch/arc/Kconfig

+2 −2
Original line number Diff line number Diff line
@@ -556,7 +556,7 @@ endmenu # "ARC Architecture Configuration" 


config ARCH_FORCE_MAX_ORDER

	int "Maximum zone order"

	default "12" if ARC_HUGEPAGE_16M

	default "11"

	default "11" if ARC_HUGEPAGE_16M

	default "10"



source "kernel/power/Kconfig"

arch/arm/Kconfig

+3 −6
Original line number Diff line number Diff line
@@ -1355,9 +1355,9 @@ config ARM_MODULE_PLTS 


config ARCH_FORCE_MAX_ORDER

	int "Maximum zone order"

	default "12" if SOC_AM33XX

	default "9" if SA1111

	default "11"

	default "11" if SOC_AM33XX

	default "8" if SA1111

	default "10"

	help

	  The kernel memory allocator divides physically contiguous memory

	  blocks into "zones", where each zone is a power of two number of
@@ -1366,9 +1366,6 @@ config ARCH_FORCE_MAX_ORDER 
	  blocks of physically contiguous memory, then you may need to

	  increase this value.



	  This config option is actually maximum order plus one. For example,

	  a value of 11 means that the largest free memory block is 2^10 pages.



config ALIGNMENT_TRAP

	def_bool CPU_CP15_MMU

	select HAVE_PROC_CPU if PROC_FS

arch/arm/configs/imx_v6_v7_defconfig

+1 −1
Original line number Diff line number Diff line
@@ -31,7 +31,7 @@ CONFIG_SOC_VF610=y 
CONFIG_SMP=y

CONFIG_ARM_PSCI=y

CONFIG_HIGHMEM=y

CONFIG_ARCH_FORCE_MAX_ORDER=14

CONFIG_ARCH_FORCE_MAX_ORDER=13

CONFIG_CMDLINE="noinitrd console=ttymxc0,115200"

CONFIG_KEXEC=y

CONFIG_CPU_FREQ=y