From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8D9CCC7EE2C for ; Thu, 25 May 2023 21:51:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241995AbjEYVvh (ORCPT ); Thu, 25 May 2023 17:51:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53212 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241965AbjEYVvd (ORCPT ); Thu, 25 May 2023 17:51:33 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DCC9A1BC for ; Thu, 25 May 2023 14:50:56 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 7698664B8F for ; Thu, 25 May 2023 21:50:23 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CF76CC433EF; Thu, 25 May 2023 21:50:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1685051422; bh=OZtsal2X9lVgaI/9FlSk7qcdvctmnz67oZWIWD18ND8=; h=Date:To:From:Subject:From; b=bX5d4gI6muj9vsUPfA5cjnTHK2ZUSNaLtCJPfn+I9na16Foj9rJs23Wxgog3XKoIa 1sCHhT1PQVbhLZT37mTAabixymxSQBwSQfnqvAENNgSnqZIn9b4L27CGMAP0Aps+26 I3a7AWG0ToxFfQHrgMtzPGoRUh5ZWlWkLUdhY4mk= Date: Thu, 25 May 2023 14:50:22 -0700 To: mm-commits@vger.kernel.org, corbet@lwn.net, sj@kernel.org, akpm@linux-foundation.org From: Andrew Morton Subject: + docs-mm-damon-design-add-sections-for-advanced-features-of-damos.patch added to mm-unstable branch Message-Id: <20230525215022.CF76CC433EF@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The patch titled Subject: Docs/mm/damon/design: add sections for advanced features of DAMOS has been added to the -mm mm-unstable branch. Its filename is docs-mm-damon-design-add-sections-for-advanced-features-of-damos.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/docs-mm-damon-design-add-sections-for-advanced-features-of-damos.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: SeongJae Park Subject: Docs/mm/damon/design: add sections for advanced features of DAMOS Date: Thu, 25 May 2023 21:43:12 +0000 Add sections for advanced features of DAMOS including quotas, prioritization, watermarks, and filters of DAMOS on the design document. Link: https://lkml.kernel.org/r/20230525214314.5204-9-sj@kernel.org Signed-off-by: SeongJae Park Cc: Jonathan Corbet Signed-off-by: Andrew Morton --- Documentation/mm/damon/design.rst | 86 ++++++++++++++++++++++++++++ 1 file changed, 86 insertions(+) --- a/Documentation/mm/damon/design.rst~docs-mm-damon-design-add-sections-for-advanced-features-of-damos +++ a/Documentation/mm/damon/design.rst @@ -272,3 +272,89 @@ the access frequency, and the age. User interest by setting minimum and maximum values of the three properties. If a region's three properties are in the ranges, DAMOS classifies it as one of the regions that the scheme is having an interest in. + + +Quotas +~~~~~~ + +DAMOS upper-bound overhead control feature. DAMOS could incur high overhead if +the target access pattern is not properly tuned. For example, if a huge memory +region having the access pattern of interest is found, applying the scheme's +action to all pages of the huge region could consume unacceptably large system +resources. Preventing such issues by tuning the access pattern could be +challenging, especially if the access patterns of the workloads are highly +dynamic. + +To mitigate that situation, DAMOS provides an upper-bound overhead control +feature called quotas. It lets users specify an upper limit of time that DAMOS +can use for applying the action, and/or a maximum bytes of memory regions that +the action can be applied within a user-specified time duration. + + +Prioritization +^^^^^^^^^^^^^^ + +A mechanism for making a good decision under the quotas. When the action +cannot be applied to all regions of interest due to the quotas, DAMOS +prioritizes regions and applies the action to only regions having high enough +priorities so that it will not exceed the quotas. + +The prioritization mechanism should be different for each action. For example, +rarely accessed (colder) memory regions would be prioritized for page-out +scheme action. In contrast, the colder regions would be deprioritized for huge +page collapse scheme action. Hence, the prioritization mechanisms for each +action are implemented in each DAMON operations set, together with the actions. + +Though the implementation is up to the DAMON operations set, it would be common +to calculate the priority using the access pattern properties of the regions. +Some users would want the mechanisms to be personalized for their specific +case. For example, some users would want the mechanism to weigh the recency +(``age``) more than the access frequency (``nr_accesses``). DAMOS allows users +to specify the weight of each access pattern property and passes the +information to the underlying mechanism. Nevertheless, how and even whether +the weight will be respected are up to the underlying prioritization mechanism +implementation. + + +Watermarks +~~~~~~~~~~ + +Conditional DAMOS (de)activation automation. Users might want DAMOS to run +only under certain situations. For example, when a sufficient amount of free +memory is guaranteed, running a scheme for proactive reclamation would only +consume unnecessary system resources. To avoid such consumption, the user would +need to manually monitor some metrics such as free memory ratio, and turn +DAMON/DAMOS on or off. + +DAMOS allows users to offload such works using three watermarks. It allows the +users to configure the metric of their interest, and three watermark values, +namely high, middle, and low. If the value of the metric becomes above the +high watermark or below the low watermark, the scheme is deactivated. If the +metric becomes below the mid watermark but above the low watermark, the scheme +is activated. If all schemes are deactivated by the watermarks, the monitoring +is also deactivated. In this case, the DAMON worker thread only periodically +checks the watermarks and therefore incurs nearly zero overhead. + + +Filters +~~~~~~~ + +Non-access pattern-based target memory regions filtering. If users run +self-written programs or have good profiling tools, they could know something +more than the kernel, such as future access patterns or some special +requirements for specific types of memory. For example, some users may know +only anonymous pages can impact their program's performance. They can also +have a list of latency-critical processes. + +To let users optimize DAMOS schemes with such special knowledge, DAMOS provides +a feature called DAMOS filters. The feature allows users to set an arbitrary +number of filters for each scheme. Each filter specifies the type of target +memory, and whether it should exclude the memory of the type (filter-out), or +all except the memory of the type (filter-in). + +As of this writing, anonymous page type and memory cgroup type are supported by +the feature. Some filter target types can require additional arguments. For +example, the memory cgroup filter type asks users to specify the file path of +the memory cgroup for the filter. Hence, users can apply specific schemes to +only anonymous pages, non-anonymous pages, pages of specific cgroups, all pages +excluding those of specific cgroups, and any combination of those. _ Patches currently in -mm which might be from sj@kernel.org are docs-mm-damon-faq-remove-old-questions.patch docs-mm-damon-maintainer-profile-fix-typos-and-grammar-errors.patch docs-mm-damon-design-add-a-section-for-overall-architecture.patch docs-mm-damon-design-update-the-layout-based-on-the-layers.patch docs-mm-damon-design-rewrite-configurable-layers.patch docs-mm-damon-design-add-a-section-for-the-relation-between-core-and-modules-layer.patch docs-mm-damon-design-add-sections-for-basic-parts-of-damos.patch docs-mm-damon-design-add-sections-for-advanced-features-of-damos.patch docs-mm-damon-design-add-a-section-for-damon-core-api.patch docs-mm-damon-design-add-a-section-for-the-modules-layer.patch