From: Jia He <jia.he@xxxxxxxxxxxxxxxx>
Subject: arm: arm64: introduce CONFIG_HAVE_MEMBLOCK_PFN_VALID
Patch series "remain and optimize memblock_next_valid_pfn on arm and
arm64", v11.
b92df1de5d28 ("mm: page_alloc: skip over regions of invalid pfns where
possible") optimized the loop in memmap_init_zone(). But it causes
possible panic bug. So Daniel Vacek reverted it later.
But as suggested by Daniel Vacek, it is fine to using memblock to skip
gaps and finding next valid frame with CONFIG_HAVE_ARCH_PFN_VALID.
More from what Daniel said:
"On arm and arm64, memblock is used by default. But generic version of
pfn_valid() is based on mem sections and memblock_next_valid_pfn() does
not always return the next valid one but skips more resulting in some
valid frames to be skipped (as if they were invalid). And that's why
kernel was eventually crashing on some !arm machines."
About the performance consideration:
As said by James in b92df1de5,
"I have tested this patch on a virtual model of a Samurai CPU with a
sparse memory map. The kernel boot time drops from 109 to 62 seconds."
Thus it would be better if we remain memblock_next_valid_pfn on arm/arm64.
Besides we can remain memblock_next_valid_pfn, there is still some room
for improvement. After this set, I can see the time overhead of
memmap_init is reduced from 27956us to 13537us in my armv8a server(QDF2400
with 96G memory, pagesize 64k). I believe arm server will benefit more if
memory is larger than TBs
Patch 1 introduces new config to make codes more generic
Patch 2 remains the memblock_next_valid_pfn on arm and arm64,this patch is
originated from b92df1de5
Patch 3 optimizes the memblock_next_valid_pfn()
This patch (of 3):
Make CONFIG_HAVE_MEMBLOCK_PFN_VALID a new config option so it can move
memblock_next_valid_pfn to generic code file. All the latter
optimizations are based on this config.
The memblock initialization time on arm/arm64 can benefit from this.
Link: http://lkml.kernel.org/r/1534907237-2982-2-git-send-email-jia.he@xxxxxxxxxxxxxxxx
Signed-off-by: Jia He <jia.he@xxxxxxxxxxxxxxxx>
Reviewed-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Cc: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx>
Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
Cc: Daniel Vacek <neelx@xxxxxxxxxx>
Cc: Eugeniu Rosca <erosca@xxxxxxxxxxxxxx>
Cc: Gioh Kim <gi-oh.kim@xxxxxxxxxxxxxxxx>
Cc: James Morse <james.morse@xxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Kemi Wang <kemi.wang@xxxxxxxxx>
Cc: Laura Abbott <labbott@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Nikolay Borisov <nborisov@xxxxxxxx>
Cc: Pavel Tatashin <pavel.tatashin@xxxxxxxxxxxxx>
Cc: Petr Tesarik <ptesarik@xxxxxxxx>
Cc: Philip Derrin <philip@cog.systems>
Cc: Russell King <linux@xxxxxxxxxxxxxxx>
Cc: Steve Capper <steve.capper@xxxxxxx>
Cc: Vladimir Murzin <vladimir.murzin@xxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Wei Yang <richard.weiyang@xxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: YASUAKI ISHIMATSU <yasu.isimatu@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/arm/Kconfig | 1 +
arch/arm64/Kconfig | 1 +
mm/Kconfig | 3 +++
3 files changed, 5 insertions(+)
--- a/arch/arm64/Kconfig~arm-arm64-introduce-config_have_memblock_pfn_valid
+++ a/arch/arm64/Kconfig
@@ -800,6 +800,7 @@ config ARCH_FLATMEM_ENABLE
config HAVE_ARCH_PFN_VALID
def_bool y
+ select HAVE_MEMBLOCK_PFN_VALID
config HW_PERF_EVENTS
def_bool y
--- a/arch/arm/Kconfig~arm-arm64-introduce-config_have_memblock_pfn_valid
+++ a/arch/arm/Kconfig
@@ -1634,6 +1634,7 @@ config ARCH_SELECT_MEMORY_MODEL
config HAVE_ARCH_PFN_VALID
def_bool ARCH_HAS_HOLES_MEMORYMODEL || !SPARSEMEM
+ select HAVE_MEMBLOCK_PFN_VALID
config HAVE_GENERIC_GUP
def_bool y
--- a/mm/Kconfig~arm-arm64-introduce-config_have_memblock_pfn_valid
+++ a/mm/Kconfig
@@ -136,6 +136,9 @@ config HAVE_MEMBLOCK_NODE_MAP
config HAVE_MEMBLOCK_PHYS_MAP
bool
+config HAVE_MEMBLOCK_PFN_VALID
+ bool
+
config HAVE_GENERIC_GUP
bool
_
