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authorMike Rapoport <rppt@linux.ibm.com>2020-12-15 06:10:15 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2020-12-15 23:13:43 +0300
commitfcd353a314213534d04193eea0bc54c4b7a3e1b0 (patch)
tree8931085bad0a39a275ea6183388924b288d504cb /arch/m68k/Kconfig.cpu
parent4bfc848e0981fcd35db00fe1c6581560689f6dc7 (diff)
downloadlinux-fcd353a314213534d04193eea0bc54c4b7a3e1b0.tar.xz
m68k: deprecate DISCONTIGMEM
DISCONTIGMEM was intended to provide more efficient support for systems with holes in their physical address space that FLATMEM did. Yet, it's overhead in terms of the memory consumption seems to overweight the savings on the unused memory map. For a ARAnyM system with 16 MBytes of FastRAM configured, the memory usage reported after page allocator initialization is Memory: 23828K/30720K available (3206K kernel code, 535K rwdata, 936K rodata, 768K init, 193K bss, 6892K reserved, 0K cma-reserved) and with DISCONTIGMEM disabled and with relatively large hole in the memory map it is: Memory: 23864K/30720K available (3197K kernel code, 516K rwdata, 936K rodata, 764K init, 179K bss, 6856K reserved, 0K cma-reserved) Moreover, since m68k already has custom pfn_valid() it is possible to define HAVE_ARCH_PFN_VALID to enable freeing of unused memory map. The minimal size of a hole that can be freed should not be less than MAX_ORDER_NR_PAGES so to achieve more substantial memory savings let m68k also define custom FORCE_MAX_ZONEORDER. With FORCE_MAX_ZONEORDER set to 9 memory usage becomes: Memory: 23880K/30720K available (3197K kernel code, 516K rwdata, 936K rodata, 764K init, 179K bss, 6840K reserved, 0K cma-reserved) Link: https://lkml.kernel.org/r/20201101170454.9567-14-rppt@kernel.org Signed-off-by: Mike Rapoport <rppt@linux.ibm.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Greg Ungerer <gerg@linux-m68k.org> Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Matt Turner <mattst88@gmail.com> Cc: Meelis Roos <mroos@linux.ee> Cc: Michael Schmitz <schmitzmic@gmail.com> Cc: Russell King <linux@armlinux.org.uk> Cc: Tony Luck <tony.luck@intel.com> Cc: Vineet Gupta <vgupta@synopsys.com> Cc: Will Deacon <will@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/m68k/Kconfig.cpu')
-rw-r--r--arch/m68k/Kconfig.cpu26
1 files changed, 25 insertions, 1 deletions
diff --git a/arch/m68k/Kconfig.cpu b/arch/m68k/Kconfig.cpu
index b8884af365ae..3e70fb7a8d83 100644
--- a/arch/m68k/Kconfig.cpu
+++ b/arch/m68k/Kconfig.cpu
@@ -20,6 +20,7 @@ choice
config M68KCLASSIC
bool "Classic M68K CPU family support"
+ select HAVE_ARCH_PFN_VALID
config COLDFIRE
bool "Coldfire CPU family support"
@@ -377,11 +378,34 @@ config SINGLE_MEMORY_CHUNK
help
Ignore all but the first contiguous chunk of physical memory for VM
purposes. This will save a few bytes kernel size and may speed up
- some operations. Say N if not sure.
+ some operations.
+ When this option os set to N, you may want to lower "Maximum zone
+ order" to save memory that could be wasted for unused memory map.
+ Say N if not sure.
config ARCH_DISCONTIGMEM_ENABLE
+ depends on BROKEN
def_bool MMU && !SINGLE_MEMORY_CHUNK
+config FORCE_MAX_ZONEORDER
+ int "Maximum zone order" if ADVANCED
+ depends on !SINGLE_MEMORY_CHUNK
+ default "11"
+ help
+ The kernel memory allocator divides physically contiguous memory
+ blocks into "zones", where each zone is a power of two number of
+ pages. This option selects the largest power of two that the kernel
+ keeps in the memory allocator. If you need to allocate very large
+ blocks of physically contiguous memory, then you may need to
+ increase this value.
+
+ For systems that have holes in their physical address space this
+ value also defines the minimal size of the hole that allows
+ freeing unused memory map.
+
+ 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 060_WRITETHROUGH
bool "Use write-through caching for 68060 supervisor accesses"
depends on ADVANCED && M68060