From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f198.google.com (mail-qk0-f198.google.com [209.85.220.198]) by kanga.kvack.org (Postfix) with ESMTP id 641B66B0009 for ; Tue, 24 Apr 2018 02:40:50 -0400 (EDT) Received: by mail-qk0-f198.google.com with SMTP id p190so7783443qkc.17 for ; Mon, 23 Apr 2018 23:40:50 -0700 (PDT) Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com. [148.163.156.1]) by mx.google.com with ESMTPS id m21-v6si12928374qtf.343.2018.04.23.23.40.49 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 23 Apr 2018 23:40:49 -0700 (PDT) Received: from pps.filterd (m0098396.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w3O6emum054701 for ; Tue, 24 Apr 2018 02:40:48 -0400 Received: from e06smtp11.uk.ibm.com (e06smtp11.uk.ibm.com [195.75.94.107]) by mx0a-001b2d01.pphosted.com with ESMTP id 2hhw8tnvhk-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 24 Apr 2018 02:40:48 -0400 Received: from localhost by e06smtp11.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 24 Apr 2018 07:40:45 +0100 From: Mike Rapoport Subject: [PATCH 5/7] docs/vm: ksm: update stable_node_chains_prune_millisecs description Date: Tue, 24 Apr 2018 09:40:26 +0300 In-Reply-To: <1524552028-7017-1-git-send-email-rppt@linux.vnet.ibm.com> References: <1524552028-7017-1-git-send-email-rppt@linux.vnet.ibm.com> Message-Id: <1524552028-7017-6-git-send-email-rppt@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Jonathan Corbet Cc: Andrew Morton , Andrea Arcangeli , linux-doc , linux-mm , lkml , Mike Rapoport Make the description of stable_node_chains_prune_millisecs sysfs parameter less implementation aware and add a few words about this parameter in the "Design" section. Signed-off-by: Mike Rapoport --- Documentation/vm/ksm.rst | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-) diff --git a/Documentation/vm/ksm.rst b/Documentation/vm/ksm.rst index 00961b8..18d7c71 100644 --- a/Documentation/vm/ksm.rst +++ b/Documentation/vm/ksm.rst @@ -150,14 +150,12 @@ max_page_sharing traversals are always schedule friendly themselves. stable_node_chains_prune_millisecs - How frequently to walk the whole list of stable_node "dups" - linked in the stable_node "chains" in order to prune stale - stable_nodes. Smaller milllisecs values will free up the KSM - metadata with lower latency, but they will make ksmd use more - CPU during the scan. This only applies to the stable_node - chains so it's a noop if not a single KSM page hit the - ``max_page_sharing`` yet (there would be no stable_node chains in - such case). + specifies how frequently KSM checks the metadata of the pages + that hit the deduplication limit for stale information. + Smaller milllisecs values will free up the KSM metadata with + lower latency, but they will make ksmd use more CPU during the + scan. It's a noop if not a single KSM page hit the + ``max_page_sharing`` yet. The effectiveness of KSM and MADV_MERGEABLE is shown in ``/sys/kernel/mm/ksm/``: @@ -249,6 +247,11 @@ deduplication factor at the expense of slower worst case for rmap walks for any KSM page which can happen during swapping, compaction, NUMA balancing and page migration. +The whole list of stable_node "dups" linked in the stable_node +"chains" is scanned periodically in order to prune stale stable_nodes. +The frequency of such scans is defined by +``stable_node_chains_prune_millisecs`` sysfs tunable. + Reference --------- .. kernel-doc:: mm/ksm.c -- 2.7.4