From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f200.google.com (mail-pf0-f200.google.com [209.85.192.200]) by kanga.kvack.org (Postfix) with ESMTP id BA7996B0069 for ; Fri, 20 Jan 2017 10:52:12 -0500 (EST) Received: by mail-pf0-f200.google.com with SMTP id 204so101963635pfx.1 for ; Fri, 20 Jan 2017 07:52:12 -0800 (PST) Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com. [148.163.156.1]) by mx.google.com with ESMTPS id u3si7209374plj.76.2017.01.20.07.52.11 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 20 Jan 2017 07:52:11 -0800 (PST) Received: from pps.filterd (m0098393.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v0KFnVxn100371 for ; Fri, 20 Jan 2017 10:52:11 -0500 Received: from e06smtp08.uk.ibm.com (e06smtp08.uk.ibm.com [195.75.94.104]) by mx0a-001b2d01.pphosted.com with ESMTP id 2833bgg0fk-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Fri, 20 Jan 2017 10:52:10 -0500 Received: from localhost by e06smtp08.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 20 Jan 2017 15:52:07 -0000 From: Claudio Imbrenda Subject: [PATCH v3 1/1] mm/ksm: documentation for coloured zero pages deduplication Date: Fri, 20 Jan 2017 16:52:02 +0100 Message-Id: <1484927522-1964-1-git-send-email-imbrenda@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org Cc: borntraeger@de.ibm.com, hughd@google.com, aarcange@redhat.com, chrisw@sous-sol.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org This patch adds the needed documentation for the use_zero_pages property. Signed-off-by: Claudio Imbrenda --- Documentation/vm/ksm.txt | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/Documentation/vm/ksm.txt b/Documentation/vm/ksm.txt index f34a8ee..0c64a81d 100644 --- a/Documentation/vm/ksm.txt +++ b/Documentation/vm/ksm.txt @@ -80,6 +80,20 @@ run - set 0 to stop ksmd from running but keep merged pages, Default: 0 (must be changed to 1 to activate KSM, except if CONFIG_SYSFS is disabled) +use_zero_pages - specifies whether empty pages (i.e. allocated pages + that only contain zeroes) should be treated specially. + When set to 1, empty pages are merged with the kernel + zero page(s) instead of with each other as it would + happen normally. This can improve the performance on + architectures with coloured zero pages, depending on + the workload. Care should be taken when enabling this + setting, as it can potentially degrade the performance + of KSM for some workloads, for example if the checksums + of pages candidate for merging match the checksum of + an empty page. This setting can be changed at any time, + it is only effective for pages merged after the change. + Default: 0 (normal KSM behaviour as in earlier releases) + The effectiveness of KSM and MADV_MERGEABLE is shown in /sys/kernel/mm/ksm/: pages_shared - how many shared pages are being used -- 1.9.1 -- 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