Commit 423bec43 authored by Nishanth Aravamudan's avatar Nishanth Aravamudan Committed by Linus Torvalds

Documentation: correct overcommit caveat in hugetlbpage.txt

As shown by Gurudas Pai recently, we can put hugepages into the surplus
state (by echo 0 > /proc/sys/vm/nr_hugepages), even when
/proc/sys/vm/nr_overcommit_hugepages is 0. This is actually correct, to
allow the original goal (shrink the static pool to 0) to succeed (we are
converting hugepages to surplus because they are in use). However, the
documentation does not accurately reflect this case. Update it.
Signed-off-by: default avatarNishanth Aravamudan <nacc@us.ibm.com>
Acked-by: default avatarAndy Whitcroft <apw@shadowen.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 91446b06
...@@ -88,10 +88,9 @@ hugepages from the buddy allocator, if the normal pool is exhausted. As ...@@ -88,10 +88,9 @@ hugepages from the buddy allocator, if the normal pool is exhausted. As
these surplus hugepages go out of use, they are freed back to the buddy these surplus hugepages go out of use, they are freed back to the buddy
allocator. allocator.
Caveat: Shrinking the pool via nr_hugepages while a surplus is in effect Caveat: Shrinking the pool via nr_hugepages such that it becomes less
will allow the number of surplus huge pages to exceed the overcommit than the number of hugepages in use will convert the balance to surplus
value, as the pool hugepages (which must have been in use for a surplus huge pages even if it would exceed the overcommit value. As long as
hugepages to be allocated) will become surplus hugepages. As long as
this condition holds, however, no more surplus huge pages will be this condition holds, however, no more surplus huge pages will be
allowed on the system until one of the two sysctls are increased allowed on the system until one of the two sysctls are increased
sufficiently, or the surplus huge pages go out of use and are freed. sufficiently, or the surplus huge pages go out of use and are freed.
......
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