Documentation/vm/transhuge.txt: add information about max_ptes_swap

max_ptes_swap specifies how many pages can be brought in from swap when
collapsing a group of pages into a transparent huge page.

/sys/kernel/mm/transparent_hugepage/khugepaged/max_ptes_swap

A higher value can cause excessive swap IO and waste memory.  A lower
value can prevent THPs from being collapsed, resulting fewer pages being
collapsed into THPs, and lower memory access performance.

Signed-off-by: Ebru Akagunduz <ebru.akagunduz@gmail.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/Documentation/vm/transhuge.txt b/Documentation/vm/transhuge.txt
index 8143b9e8373db41746330c468dede07acfd96b56..8a282687ee069ffc415e3c717d0991c6baf7f7fc 100644 (file)
--- a/Documentation/vm/transhuge.txt
+++ b/Documentation/vm/transhuge.txt
@@ -170,6 +170,16 @@ A lower value leads to gain less thp performance. Value of
 max_ptes_none can waste cpu time very little, you can
 ignore it.
 
+max_ptes_swap specifies how many pages can be brought in from
+swap when collapsing a group of pages into a transparent huge page.
+
+/sys/kernel/mm/transparent_hugepage/khugepaged/max_ptes_swap
+
+A higher value can cause excessive swap IO and waste
+memory. A lower value can prevent THPs from being
+collapsed, resulting fewer pages being collapsed into
+THPs, and lower memory access performance.
+
 == Boot parameter ==
 
 You can change the sysfs boot time defaults of Transparent Hugepage