diff options
author | Maciej S. Szmigiero <maciej.szmigiero@oracle.com> | 2022-03-22 14:47:43 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2022-03-22 15:57:11 -0700 |
commit | cb325ddde5616219848ac0e100a781919a0ce55b (patch) | |
tree | 677bd45c77d094f0ff54efb3dd5cf5681856fce2 | |
parent | bd55b0c2d64e84a75575f548a33a3dfecc135b65 (diff) | |
download | linux-cb325ddde5616219848ac0e100a781919a0ce55b.tar.bz2 |
mm/zswap.c: allow handling just same-value filled pages
Zswap has an ability to efficiently store same-value filled pages, which
can be turned on and off using the "same_filled_pages_enabled"
parameter.
However, there is currently no way to enable just this (lightweight)
functionality, while not making use of the whole compressed page storage
machinery.
Add a "non_same_filled_pages_enabled" parameter which allows disabling
handling of pages that aren't same-value filled. This way zswap can be
run in such lightweight same-value filled pages only mode.
Link: https://lkml.kernel.org/r/7dbafa963e8bab43608189abbe2067f4b9287831.1641247624.git.maciej.szmigiero@oracle.com
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-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) { |