From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f198.google.com (mail-pf0-f198.google.com [209.85.192.198]) by kanga.kvack.org (Postfix) with ESMTP id B120C6B028A for ; Wed, 6 Dec 2017 06:49:00 -0500 (EST) Received: by mail-pf0-f198.google.com with SMTP id y62so2664783pfd.3 for ; Wed, 06 Dec 2017 03:49:00 -0800 (PST) Received: from mailout1.samsung.com (mailout1.samsung.com. [203.254.224.24]) by mx.google.com with ESMTPS id d126si1954381pfg.11.2017.12.06.03.48.56 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 06 Dec 2017 03:48:56 -0800 (PST) Received: from epcas5p2.samsung.com (unknown [182.195.41.40]) by mailout1.samsung.com (KnoxPortal) with ESMTP id 20171206114854epoutp01620e4f01f9e3e0e97a56844c9d78fd8f~9sifhGO552866728667epoutp01P for ; Wed, 6 Dec 2017 11:48:54 +0000 (GMT) Mime-Version: 1.0 Subject: [PATCH v2] zswap: Update with same-value filled page feature Reply-To: srividya.dr@samsung.com From: Srividya Desireddy In-Reply-To: <20171129153437epcms5p64b04efa370cc42bb0f9e5677e298704e@epcms5p6> Message-ID: <20171206114852epcms5p6973b02a9f455d5d3c765eafda0fe2631@epcms5p6> Date: Wed, 06 Dec 2017 11:48:52 +0000 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="utf-8" References: <20171129153437epcms5p64b04efa370cc42bb0f9e5677e298704e@epcms5p6> <20171018104832epcms5p1b2232e2236258de3d03d1344dde9fce0@epcms5p1> <20171120154648.6c2f96804c4c1668bd8d572a@linux-foundation.org> Sender: owner-linux-mm@kvack.org List-ID: To: Dan Streetman , "sjenning@redhat.com" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Srividya Desireddy Cc: Dinakar Reddy Pathireddy , RAJIB BASU , Srikanth Mandalapu , SHARAN ALLUR , JUHUN KIM , "srividya.desireddy@gmail.com" From: Srividya Desireddy 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 --- 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org