On Wed, Dec 6, 2017 at 6:48 AM, Srividya Desireddy <srividya...@samsung.com> wrote: > From: Srividya Desireddy <srividya...@samsung.com> > Date: Wed, 6 Dec 2017 16:29:50 +0530 > Subject: [PATCH v2] zswap: Update with same-value filled page feature > > Changes since v1: > Updated to clarify about zswap.same_filled_pages_enabled parameter. > > Updated zswap document with details on same-value filled > pages identification feature. > The usage of zswap.same_filled_pages_enabled module parameter > is explained. > > Signed-off-by: Srividya Desireddy <srividya...@samsung.com>
Acked-by: Dan Streetman <ddstr...@ieee.org> > --- > Documentation/vm/zswap.txt | 22 +++++++++++++++++++++- > 1 file changed, 21 insertions(+), 1 deletion(-) > > diff --git a/Documentation/vm/zswap.txt b/Documentation/vm/zswap.txt > index 89fff7d..0b3a114 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. > -- > 2.7.4 >
