From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-5.8 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham autolearn_force=no version=3.4.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id C097D7DD31 for ; Tue, 24 Apr 2018 06:40:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756025AbeDXGkn (ORCPT ); Tue, 24 Apr 2018 02:40:43 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:57600 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755943AbeDXGkl (ORCPT ); Tue, 24 Apr 2018 02:40:41 -0400 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 w3O6eB7d052061 for ; Tue, 24 Apr 2018 02:40:41 -0400 Received: from e06smtp12.uk.ibm.com (e06smtp12.uk.ibm.com [195.75.94.108]) by mx0a-001b2d01.pphosted.com with ESMTP id 2hhw8tnvb1-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 24 Apr 2018 02:40:40 -0400 Received: from localhost by e06smtp12.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Tue, 24 Apr 2018 07:40:34 +0100 Received: from d06av21.portsmouth.uk.ibm.com (d06av21.portsmouth.uk.ibm.com [9.149.105.232]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w3O6eXfb7733538; Tue, 24 Apr 2018 06:40:33 GMT Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 46E125204D; Tue, 24 Apr 2018 06:31:13 +0100 (BST) Received: from rapoport-lnx (unknown [9.148.8.99]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTPS id B795B52049; Tue, 24 Apr 2018 06:31:11 +0100 (BST) Received: by rapoport-lnx (sSMTP sendmail emulation); Tue, 24 Apr 2018 09:40:31 +0300 From: Mike Rapoport To: Jonathan Corbet Cc: Andrew Morton , Andrea Arcangeli , linux-doc , linux-mm , lkml , Mike Rapoport Subject: [PATCH 1/7] mm/ksm: docs: extend overview comment and make it "DOC:" Date: Tue, 24 Apr 2018 09:40:22 +0300 X-Mailer: git-send-email 2.7.4 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> X-TM-AS-GCONF: 00 x-cbid: 18042406-0008-0000-0000-000004EE858A X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18042406-0009-0000-0000-00001E82ACCA Message-Id: <1524552028-7017-2-git-send-email-rppt@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-04-24_01:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1804240067 Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org The existing comment provides a good overview of KSM implementation. Let's update it to reflect recent additions of "chain" and "dup" variants of the stable tree nodes and mark it as "DOC:" for inclusion into the KSM documentation. Signed-off-by: Mike Rapoport --- mm/ksm.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) diff --git a/mm/ksm.c b/mm/ksm.c index 58c2741..54155b1 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -51,7 +51,9 @@ #define DO_NUMA(x) do { } while (0) #endif -/* +/** + * DOC: Overview + * * A few notes about the KSM scanning process, * to make it easier to understand the data structures below: * @@ -67,6 +69,21 @@ * this tree is fully assured to be working (except when pages are unmapped), * and therefore this tree is called the stable tree. * + * The stable tree node includes information required for reverse + * mapping from a KSM page to virtual addresses that map this page. + * + * In order to avoid large latencies of the rmap walks on KSM pages, + * KSM maintains two types of nodes in the stable tree: + * + * * the regular nodes that keep the reverse mapping structures in a + * linked list + * * the "chains" that link nodes ("dups") that represent the same + * write protected memory content, but each "dup" corresponds to a + * different KSM page copy of that content + * + * Internally, the regular nodes, "dups" and "chains" are represented + * using the same :c:type:`struct stable_node` structure. + * * In addition to the stable tree, KSM uses a second data structure called the * unstable tree: this tree holds pointers to pages which have been found to * be "unchanged for a period of time". The unstable tree sorts these pages -- 2.7.4 -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html