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authorOscar Salvador <osalvador@suse.de>2021-05-04 18:39:48 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2021-05-05 11:27:27 -0700
commite3a9d9fcc3315993de2e9fcd7ea82fab84433815 (patch)
tree0ae5712c9f1a5b34f8f485bf05887e983b652d1c /Documentation
parent4a3e5de9c4ec41bb0684b0d4e0c16abc39617d88 (diff)
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>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/admin-guide/kernel-parameters.txt17
1 files changed, 17 insertions, 0 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 1c0a3cf6fcc9..d93fbc1c1917 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -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>