The patch titled
Subject: mm,memory_hotplug: add kernel boot option to enable memmap_on_memory
has been added to the -mm tree. Its filename is
mmmemory_hotplug-add-kernel-boot-option-to-enable-memmap_on_memory.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mmmemory_hotplug-add-kernel-boot-option-to-enable-memmap_on_memory.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mmmemory_hotplug-add-kernel-boot-option-to-enable-memmap_on_memory.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Oscar Salvador <osalvador@xxxxxxx>
Subject: 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@xxxxxxx
Signed-off-by: Oscar Salvador <osalvador@xxxxxxx>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Anshuman Khandual <anshuman.khandual@xxxxxxx>
Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/admin-guide/kernel-parameters.txt | 17 ++++++++++++++
mm/Makefile | 5 +++-
mm/memory_hotplug.c | 10 +++++++-
3 files changed, 30 insertions(+), 2 deletions(-)
--- a/Documentation/admin-guide/kernel-parameters.txt~mmmemory_hotplug-add-kernel-boot-option-to-enable-memmap_on_memory
+++ a/Documentation/admin-guide/kernel-parameters.txt
@@ -2794,6 +2794,23 @@
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>
--- a/mm/Makefile~mmmemory_hotplug-add-kernel-boot-option-to-enable-memmap_on_memory
+++ a/mm/Makefile
@@ -58,9 +58,13 @@ obj-y := filemap.o mempool.o oom_kill.
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
--- a/mm/memory_hotplug.c~mmmemory_hotplug-add-kernel-boot-option-to-enable-memmap_on_memory
+++ a/mm/memory_hotplug.c
@@ -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.
_
Patches currently in -mm which might be from osalvador@xxxxxxx are
x86-vmemmap-drop-handling-of-4k-unaligned-vmemmap-range.patch
x86-vmemmap-drop-handling-of-1gb-vmemmap-ranges.patch
x86-vmemmap-handle-unpopulated-sub-pmd-ranges.patch
x86-vmemmap-handle-unpopulated-sub-pmd-ranges-fix.patch
x86-vmemmap-optimize-for-consecutive-sections-in-partial-populated-pmds.patch
mmpage_alloc-bail-out-earlier-on-enomem-in-alloc_contig_migrate_range.patch
mmcompaction-let-isolate_migratepages_rangeblock-return-error-codes.patch
mmhugetlb-drop-clearing-of-flag-from-prep_new_huge_page.patch
mmhugetlb-split-prep_new_huge_page-functionality.patch
mm-make-alloc_contig_range-handle-free-hugetlb-pages.patch
mm-make-alloc_contig_range-handle-in-use-hugetlb-pages.patch
mmpage_alloc-drop-unnecessary-checks-from-pfn_range_valid_contig.patch
drivers-base-memory-introduce-memory_block_onlineoffline.patch
mmmemory_hotplug-relax-fully-spanned-sections-check.patch
mmmemory_hotplug-allocate-memmap-from-the-added-memory-range.patch
acpimemhotplug-enable-mhp_memmap_on_memory-when-supported.patch
mmmemory_hotplug-add-kernel-boot-option-to-enable-memmap_on_memory.patch
x86-kconfig-introduce-arch_mhp_memmap_on_memory_enable.patch
arm64-kconfig-introduce-arch_mhp_memmap_on_memory_enable.patch
