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[23.128.96.35]) by mx.google.com with ESMTPS id h5-20020a170902680500b001ab29e00303si5185016plk.426.2023.09.27.10.06.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 27 Sep 2023 10:06:52 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.35 as permitted sender) client-ip=23.128.96.35; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.35 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: from out1.vger.email (depot.vger.email [IPv6:2620:137:e000::3:0]) by groat.vger.email (Postfix) with ESMTP id 2237980D0815; Wed, 27 Sep 2023 09:23:17 -0700 (PDT) X-Virus-Status: Clean X-Virus-Scanned: clamav-milter 0.103.10 at groat.vger.email Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231659AbjI0QWy (ORCPT + 19 others); Wed, 27 Sep 2023 12:22:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36604 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231463AbjI0QWr (ORCPT ); Wed, 27 Sep 2023 12:22:47 -0400 Received: from 66-220-144-179.mail-mxout.facebook.com (66-220-144-179.mail-mxout.facebook.com [66.220.144.179]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6C1229C for ; Wed, 27 Sep 2023 09:22:46 -0700 (PDT) Received: by devbig1114.prn1.facebook.com (Postfix, from userid 425415) id 5401DCA4DC14; Wed, 27 Sep 2023 09:22:32 -0700 (PDT) From: Stefan Roesch To: kernel-team@fb.com Cc: shr@devkernel.io, akpm@linux-foundation.org, david@redhat.com, hannes@cmpxchg.org, riel@surriel.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v4 3/4] mm/ksm: document smart scan mode Date: Wed, 27 Sep 2023 09:22:21 -0700 Message-Id: <20230927162222.3827551-4-shr@devkernel.io> X-Mailer: git-send-email 2.39.3 In-Reply-To: <20230927162222.3827551-1-shr@devkernel.io> References: <20230927162222.3827551-1-shr@devkernel.io> MIME-Version: 1.0 X-Spam-Status: No, score=-0.8 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on groat.vger.email Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (groat.vger.email [0.0.0.0]); Wed, 27 Sep 2023 09:23:17 -0700 (PDT) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1778211265292352292 X-GMAIL-MSGID: 1778211265292352292 This adds documentation for the smart scan mode of KSM. Signed-off-by: Stefan Roesch Reviewed-by: David Hildenbrand --- Documentation/admin-guide/mm/ksm.rst | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/Documentation/admin-guide/mm/ksm.rst b/Documentation/admin-guide/mm/ksm.rst index 776f244bdae4..2b38a8bb08af 100644 --- a/Documentation/admin-guide/mm/ksm.rst +++ b/Documentation/admin-guide/mm/ksm.rst @@ -155,6 +155,15 @@ stable_node_chains_prune_millisecs scan. It's a noop if not a single KSM page hit the ``max_page_sharing`` yet. +smart_scan + Historically KSM checked every candidate page for each scan. It did + not take into account historic information. When smart scan is + enabled, pages that have previously not been de-duplicated get + skipped. How often these pages are skipped depends on how often + de-duplication has already been tried and failed. By default this + optimization is enabled. The ``pages_skipped`` metric shows how + effective the setting is. + The effectiveness of KSM and MADV_MERGEABLE is shown in ``/sys/kernel/mm/ksm/``: general_profit