mm/zswap.c: allow handling just same-value filled pages

[linux-2.6-microblaze.git] / Documentation / admin-guide / mm / zswap.rst

diff --git a/Documentation/admin-guide/mm/zswap.rst b/Documentation/admin-guide/mm/zswap.rst
index 8edb8d5..6e6f7b0 100644 (file)
--- a/Documentation/admin-guide/mm/zswap.rst
+++ b/Documentation/admin-guide/mm/zswap.rst
@@ -130,9 +130,25 @@ attribute, e.g.::
        echo 1 > /sys/module/zswap/parameters/same_filled_pages_enabled
 
 When zswap same-filled page identification is disabled at runtime, it will stop
-checking for the same-value filled pages during store operation. However, the
-existing pages which are marked as same-value filled pages remain stored
-unchanged in zswap until they are either loaded or invalidated.
+checking for the same-value filled pages during store operation.
+In other words, every page will be then considered non-same-value filled.
+However, the existing pages which are marked as same-value filled pages remain
+stored unchanged in zswap until they are either loaded or invalidated.
+
+In some circumstances it might be advantageous to make use of just the zswap
+ability to efficiently store same-filled pages without enabling the whole
+compressed page storage.
+In this case the handling of non-same-value pages by zswap (enabled by default)
+can be disabled by setting the ``non_same_filled_pages_enabled`` attribute
+to 0, e.g. ``zswap.non_same_filled_pages_enabled=0``.
+It can also be enabled and disabled at runtime using the sysfs
+``non_same_filled_pages_enabled`` attribute, e.g.::
+
+       echo 1 > /sys/module/zswap/parameters/non_same_filled_pages_enabled
+
+Disabling both ``zswap.same_filled_pages_enabled`` and
+``zswap.non_same_filled_pages_enabled`` effectively disables accepting any new
+pages by zswap.
 
 To prevent zswap from shrinking pool when zswap is full and there's a high
 pressure on swap (this will result in flipping pages in and out zswap pool