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mm,memory_hotplug: add kernel boot option to enable memmap_on_memory 

Self stored memmap leads to a sparse memory situation which is
unsuitable for workloads that requires large contiguous memory chunks,
so make this an opt-in which needs to be explicitly enabled.

To control this, let memory_hotplug have its own memory space, as
suggested by David, so we can add memory_hotplug.memmap_on_memory
parameter.

Link: https://lkml.kernel.org/r/20210421102701.25051-7-osalvador@suse.de
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oscar Salvador 2021-05-04 18:39:48 -07:00 committed by Linus Torvalds
parent 4a3e5de9c4
commit e3a9d9fcc3
3 changed files with 30 additions and 2 deletions
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17
Documentation/admin-guide/kernel-parameters.txt
View File

@ -2801,6 +2801,23 @@
seconds. Use this parameter to check at some
other rate. 0 disables periodic checking.
memory_hotplug.memmap_on_memory
[KNL,X86,ARM] Boolean flag to enable this feature.
Format: {on | off (default)}
When enabled, runtime hotplugged memory will
allocate its internal metadata (struct pages)
from the hotadded memory which will allow to
hotadd a lot of memory without requiring
additional memory to do so.
This feature is disabled by default because it
has some implication on large (e.g. GB)
allocations in some configurations (e.g. small
memory blocks).
The state of the flag can be read in
/sys/module/memory_hotplug/parameters/memmap_on_memory.
Note that even when enabled, there are a few cases where
the feature is not effective.
memtest= [KNL,X86,ARM,PPC] Enable memtest
Format: <integer>
default : 0 <disable>

5
mm/Makefile
View File

@ -58,9 +58,13 @@ obj-y := filemap.o mempool.o oom_kill.o fadvise.o \
page-alloc-y := page_alloc.o
page-alloc-$(CONFIG_SHUFFLE_PAGE_ALLOCATOR) += shuffle.o
# Give 'memory_hotplug' its own module-parameter namespace
memory-hotplug-$(CONFIG_MEMORY_HOTPLUG) += memory_hotplug.o
obj-y += page-alloc.o
obj-y += init-mm.o
obj-y += memblock.o
obj-y += $(memory-hotplug-y)
ifdef CONFIG_MMU
obj-$(CONFIG_ADVISE_SYSCALLS) += madvise.o
@ -83,7 +87,6 @@ obj-$(CONFIG_SLUB) += slub.o
obj-$(CONFIG_KASAN) += kasan/
obj-$(CONFIG_KFENCE) += kfence/
obj-$(CONFIG_FAILSLAB) += failslab.o
obj-$(CONFIG_MEMORY_HOTPLUG) += memory_hotplug.o
obj-$(CONFIG_MEMTEST) += memtest.o
obj-$(CONFIG_MIGRATION) += migrate.o
obj-$(CONFIG_TRANSPARENT_HUGEPAGE) += huge_memory.o khugepaged.o

10
mm/memory_hotplug.c
View File

@ -42,7 +42,15 @@
#include "internal.h"
#include "shuffle.h"
static bool memmap_on_memory;
/*
* memory_hotplug.memmap_on_memory parameter
*/
static bool memmap_on_memory __ro_after_init;
#ifdef CONFIG_MHP_MEMMAP_ON_MEMORY
module_param(memmap_on_memory, bool, 0444);
MODULE_PARM_DESC(memmap_on_memory, "Enable memmap on memory for memory hotplug");
#endif
/*
* online_page_callback contains pointer to current page onlining function.