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| author | Srividya Desireddy <srividya.dr@samsung.com> | 2017-12-14 15:32:45 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-12-14 16:00:48 -0800 |
| commit | 51f73fffbf30b335d036ab356b67b05e16e26585 (patch) | |
| tree | 575b446ca42261f0c70278640cf58ff4bb15c136 /Documentation/vm | |
| parent | 3756f6401c302617c5e091081ca4d26ab604bec5 (diff) | |
| download | linux-51f73fffbf30b335d036ab356b67b05e16e26585.tar.bz2 | |
Documentation/vm/zswap.txt: update with same-value filled page feature
Update zswap document with details on same-value filled pages
identification feature. The usage of zswap.same_filled_pages_enabled
module parameter is explained.
Link: http://lkml.kernel.org/r/20171206114852epcms5p6973b02a9f455d5d3c765eafda0fe2631@epcms5p6
Signed-off-by: Srividya Desireddy <srividya.dr@samsung.com>
Acked-by: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/vm')
| -rw-r--r-- | Documentation/vm/zswap.txt | 22 |
1 files changed, 21 insertions, 1 deletions
diff --git a/Documentation/vm/zswap.txt b/Documentation/vm/zswap.txt index 89fff7d611cc..0b3a1148f9f0 100644 --- a/Documentation/vm/zswap.txt +++ b/Documentation/vm/zswap.txt @@ -98,5 +98,25 @@ request is made for a page in an old zpool, it is uncompressed using its original compressor. Once all pages are removed from an old zpool, the zpool and its compressor are freed. +Some of the pages in zswap are same-value filled pages (i.e. contents of the +page have same value or repetitive pattern). These pages include zero-filled +pages and they are handled differently. During store operation, a page is +checked if it is a same-value filled page before compressing it. If true, the +compressed length of the page is set to zero and the pattern or same-filled +value is stored. + +Same-value filled pages identification feature is enabled by default and can be +disabled at boot time by setting the "same_filled_pages_enabled" attribute to 0, +e.g. zswap.same_filled_pages_enabled=0. It can also be enabled and disabled at +runtime using the sysfs "same_filled_pages_enabled" 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. + A debugfs interface is provided for various statistic about pool size, number -of pages stored, and various counters for the reasons pages are rejected. +of pages stored, same-value filled pages and various counters for the reasons +pages are rejected. |