diff options
| -rw-r--r-- | Documentation/admin-guide/mm/zswap.rst | 22 | ||||
| -rw-r--r-- | mm/zswap.c | 15 |
2 files changed, 33 insertions, 4 deletions
diff --git a/Documentation/admin-guide/mm/zswap.rst b/Documentation/admin-guide/mm/zswap.rst index 8edb8d578caf..6e6f7b0d6562 100644 --- 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 diff --git a/mm/zswap.c b/mm/zswap.c index cdf6950fcb2e..3efd8cae315e 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -120,11 +120,19 @@ static unsigned int zswap_accept_thr_percent = 90; /* of max pool size */ module_param_named(accept_threshold_percent, zswap_accept_thr_percent, uint, 0644); -/* Enable/disable handling same-value filled pages (enabled by default) */ +/* + * Enable/disable handling same-value filled pages (enabled by default). + * If disabled every page is considered non-same-value filled. + */ static bool zswap_same_filled_pages_enabled = true; module_param_named(same_filled_pages_enabled, zswap_same_filled_pages_enabled, bool, 0644); +/* Enable/disable handling non-same-value filled pages (enabled by default) */ +static bool zswap_non_same_filled_pages_enabled = true; +module_param_named(non_same_filled_pages_enabled, zswap_non_same_filled_pages_enabled, + bool, 0644); + /********************************* * data structures **********************************/ @@ -1147,6 +1155,11 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset, kunmap_atomic(src); } + if (!zswap_non_same_filled_pages_enabled) { + ret = -EINVAL; + goto freepage; + } + /* if entry is successfully added, it keeps the reference */ entry->pool = zswap_pool_current_get(); if (!entry->pool) { |