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From: Srividya Desireddy <srividya.dr@samsung.com>
To: Dan Streetman <ddstreet@ieee.org>,
	"sjenning@redhat.com" <sjenning@redhat.com>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Srividya Desireddy <srividya.dr@samsung.com>
Cc: Dinakar Reddy Pathireddy <dinakar.p@samsung.com>,
	RAJIB BASU <rajib.basu@samsung.com>,
	Srikanth Mandalapu <srikanth.m@samsung.com>,
	SHARAN ALLUR <sharan.allur@samsung.com>,
	JUHUN KIM <juhunkim@samsung.com>,
	"srividya.desireddy@gmail.com" <srividya.desireddy@gmail.com>
Subject: [PATCH v2] zswap: Update with same-value filled page feature
Date: Wed, 06 Dec 2017 11:48:52 +0000
Message-ID: <20171206114852epcms5p6973b02a9f455d5d3c765eafda0fe2631@epcms5p6> (raw)
In-Reply-To: <20171129153437epcms5p64b04efa370cc42bb0f9e5677e298704e@epcms5p6>

From: Srividya Desireddy <srividya.dr@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.dr@samsung.com>
---
 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

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  parent reply index

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20171018104832epcms5p1b2232e2236258de3d03d1344dde9fce0@epcms5p1>
2017-10-18 10:48 ` [PATCH] zswap: Same-filled pages handling Srividya Desireddy
2017-10-18 12:34   ` Matthew Wilcox
2017-10-18 13:33     ` Timofey Titovets
2017-10-18 14:11       ` Matthew Wilcox
2017-10-18 20:43   ` Andi Kleen
2017-10-19  1:10     ` Matthew Wilcox
2017-10-19  4:30       ` Andi Kleen
2017-10-19 13:24         ` Matthew Wilcox
2017-10-18 21:31   ` Timofey Titovets
2017-10-19  1:08     ` Matthew Wilcox
     [not found]     ` <CGME20171018104832epcms5p1b2232e2236258de3d03d1344dde9fce0@epcms5p3>
2017-11-02 15:08       ` Srividya Desireddy
2017-11-17 22:10         ` Dan Streetman
2017-11-17 22:07     ` Dan Streetman
2017-11-17 21:27   ` Dan Streetman
2017-11-20 23:46   ` Andrew Morton
2017-11-28 11:35     ` Dan Streetman
     [not found]     ` <CGME20171018104832epcms5p1b2232e2236258de3d03d1344dde9fce0@epcms5p6>
2017-11-29 15:34       ` [PATCH] zswap: Update with same-value filled page feature Srividya Desireddy
2017-11-29 21:29         ` Dan Streetman
2017-12-06 11:48       ` Srividya Desireddy [this message]
2017-12-06 15:20         ` [PATCH v2] " Dan Streetman
     [not found]   ` <CGME20171018104832epcms5p1b2232e2236258de3d03d1344dde9fce0@epcms5p4>
2017-11-21 14:18     ` [PATCH v2] zswap: Same-filled pages handling Srividya Desireddy
2017-10-18 14:43 ` [PATCH] " Srividya Desireddy

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