From patchwork Thu Feb 17 16:19:34 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: SeongJae Park X-Patchwork-Id: 12750413 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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id D7F4CC4332F for ; Thu, 17 Feb 2022 16:19:52 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 270916B0078; Thu, 17 Feb 2022 11:19:50 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 1F8C26B007B; Thu, 17 Feb 2022 11:19:50 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 026466B007E; Thu, 17 Feb 2022 11:19:49 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0003.hostedemail.com [216.40.44.3]) by kanga.kvack.org (Postfix) with ESMTP id DADE26B0078 for ; Thu, 17 Feb 2022 11:19:49 -0500 (EST) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 9A3E08249980 for ; Thu, 17 Feb 2022 16:19:49 +0000 (UTC) X-FDA: 79152782898.08.A52ABA9 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by imf09.hostedemail.com (Postfix) with ESMTP id 09397140009 for ; Thu, 17 Feb 2022 16:19:48 +0000 (UTC) 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 ams.source.kernel.org (Postfix) with ESMTPS id 14CB4B822AC; Thu, 17 Feb 2022 16:19:47 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1B78BC340E8; Thu, 17 Feb 2022 16:19:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1645114785; bh=xRpSRW/NxZIB5tKXptMtP6Y4M91PvC3Uxhmzl6GwJ6s=; h=From:To:Cc:Subject:Date:From; b=Fxr33xJon8uAnaxViuAz6dyW9NPO/maV1BqLbEarP9CmwaaFgULoD9/nhGT3RFSkD Z8OlkZbRI7fUkuSJg07xN4Fxfk1q/I4AhwXr0dyp3hwirbxUYbmWLka17If4JwI3Q4 5KyBftpi0UDyZZhQEHU+Bia3cza3Im2pddj3o7I8jyrbMFbuA5GXEvjya0yf5E+ILe OTllDVHwH2qVZ0l0GE4m30jHgC3M1urfX6jvLWmtERSO58LvKvGcviqPRtGJqiE2Kk 9OtaqFJss0STmrxqeMtl3mGPisPHkwsYO2oCauCJhHtsWsGDPhzm9ulMERLNTZMd98 d0EaHtx5dp92Q== From: SeongJae Park To: akpm@linux-foundation.org Cc: rientjes@google.com, xhao@linux.alibaba.com, linux-damon@amazon.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, SeongJae Park Subject: [RFC PATCH 0/4] Introduce DAMON sysfs interface Date: Thu, 17 Feb 2022 16:19:34 +0000 Message-Id: <20220217161938.8874-1-sj@kernel.org> X-Mailer: git-send-email 2.17.1 MIME-Version: 1.0 X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 09397140009 X-Stat-Signature: jjkgrozt4etnxekwyyhxk7911gnwga3j Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=Fxr33xJo; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf09.hostedemail.com: domain of sj@kernel.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=sj@kernel.org X-HE-Tag: 1645114788-124128 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: DAMON's debugfs-based user interface served very well, so far. However, it unnecessarily depends on debugfs, while DAMON is not aimed to be used for only debugging. Also, the interface receives multiple values via one file. For example, schemes file receives 18 values. As a result, it is not only hard to be used, but also difficult to be extended. Especially, keeping backward compatibility of user space tools is getting only challenging. It would be better to implement another reliable and flexible interface and deprecate the debugfs interface in long term. For the reason, this patchset introduces a sysfs-based new user interface of DAMON. The idea of the new interface is, using directory hierarchies and making one file for one value. For a short example, users can do the virtual address monitoring via the interface as below: # cd /sys/kernel/mm/damon/admin/ # echo 1 > kdamonds/nr # echo 1 > kdamonds/0/contexts/nr # echo vaddr > kdamonds/0/contexts/0/damon_type # echo 1 > kdamonds/0/contexts/0/targets/nr # echo $(pidof ) > kdamonds/0/contexts/0/targets/0/pid # echo on > kdamonds/0/state Changes that will be made for dropping RFC tag ---------------------------------------------- As the RFC tag means, this is not for merged in the mainline but only for early comments. Therefore, this version is not implementing all the features of DAMON debugfs interface but only basic virtual address space monitoring. The official version of the patchset will provide all the features that DAMON debugfs interface is providing. Also, this RFC patchset lacks formal documentation. It will be a part of the official version. Future plan of DAMON debugfs interface deprecation -------------------------------------------------- Once the official version of this patchset is merged, DAMON debugfs interface development will be frozen. That is, we will keep the interface works as is now, but it will not provide any new feature of DAMON. The support will be continued only until next LTS release. After that, we will drop DAMON debugfs interface. Changes to the documentation for explicitly announcing the deprecation plan would be a part of the official version of this patchset. Main difference between DAMON_DBGFS and DAMON_SYSFS --------------------------------------------------- DAMON debugfs interface allows multiple monitoring contexts, but it asks users to turn those all on and off at once. It's not a big problem but makes the operation a little bit complex. DAMON_SYSFS allows users to turn on and off monitoring contexts individually. The Hierarchy ============= In a glance, the files hierarchy of the sysfs interface is as below. /sys/kernel/mm/damon/admin │ kdamonds │ │ nr │ │ 0/ │ │ │ state,pid │ │ │ contexts │ │ │ │ nr │ │ │ │ 0/ │ │ │ │ │ damon_type │ │ │ │ │ monitoring_attrs/ │ │ │ │ │ │ intervals/sample_us,aggr_us,update_us │ │ │ │ │ │ nr_regions/min,max │ │ │ │ │ targets/ │ │ │ │ │ │ nr │ │ │ │ │ │ 0/ │ │ │ │ │ │ │ pid │ │ │ │ │ │ │ regions/ │ │ │ │ │ │ │ │ nr │ │ │ │ │ │ │ │ 0/ │ │ │ │ │ │ │ │ │ start,end │ │ │ │ │ │ │ │ ... │ │ │ │ │ │ ... │ │ │ │ │ ... │ │ ... Root ---- The root of the DAMON sysfs is /sys/kernel/mm/damon/, and it has one directory named 'admin'. The directory contains the interface for privileged user space programs. User space tools or deamons having root permission could use this directory. In a future, sibling directories for non-root user space tools or deamons (we could allow them to do monitong of their own virtual address space) or control of in-kernel DAMON-based deamons could be created. kdamonds/ --------- The monitoring-related information including request specifications and results are called DAMON context. DAMON executes a set of the contexts with a kernel thread called kdamond (for now, only one context per kdamond is supported), and multiple kdamonds could run in parallel. This directory has files for controlling the kdamonds. In the beginning, this directory has only one file, 'nr'. Writing a number (`N`) to the file creates the number of child directories named `0` to `N-1`. Each directory represents each kdamond. kdamonds// ------------- In each kdamond directory, two files (`state` and `pid`) and one directory (`contexts`) reside. Reading `state` returns `on` if the kdamond is currently running, or `off` if it is not running. Writing `on` or `off` makes the kdamond be in the state. If the state is `on`, reading `pid` shows the pid of the kdamond thread. `contexts` directory resembles `kdamonds`. It contains files for controlling the monitoring contexts that this kdamond will execute. kdamonds//contexts/ ---------------------- In the beginning, this directory has only one file, 'nr'. Writing a number (`N`) to the file creates the number of child directories named as `0` to `N-1`. Each directory represents each monitoring context. At the moment, only one context per kdamond is supported, so only `0` or `1` can be written to the file. contexts// ------------- In each context directory, one file (`operations`) and two directories (`monitoring_attrs` and `targets`) reside. DAMON supports multiple types of monitoring operations, including those for virtual address space and physical address space. You can set and show what type of monitoring operations you want to use with the context by writing one of below keywords to, and reading the file. - vaddr: Monitor virtual address spaces of specific processes Files for specifying attributes of the monitoring including required quality and efficiency of the monitoring are in `monitoring_attrs` directory, while files for specifying to what memory regions the monitoring should be done are in `targets` directory. contexts//monitoring_attrs/ ------------------------------ In this directory, you can show two directories, `intervals` and `nr_regions`. Under `intervals` directory, three files for DAMON's sampling interval (`sample_us`), aggregation interval (`aggr_us`) and update interval (`update_us`) exist. You can set and get the values by writing to and reading from the files. Under `nr_regions` directory, two files for the lower-bound and upper-bound of DAMON's monitoring regions (`min` and `max`, respectively), which controls the monitoring overhead, reside. You can set and get the values by writing to and rading from the files. For more details about the intervals and monitoring regions range, please read the Design document[1]. [1] https://docs.kernel.org/vm/damon/design.html contexts//targets/ --------------------- In the beginning, this directory has only one file, 'nr'. Writing a number (`N`) to the file creates the number of child directories named `0` to `N-1`. Each directory represents each monitoring target. targets// ------------ In each target directory, one file (`pid`) exists. You can make the context to monitor the virtual address space of a process by writing the pid of the process to the file, and show what process's virtual address space the context is set to monitor by reading the file. SeongJae Park (4): mm/damon: Implement a sysfs-based DAMON user interface mm/damon/core: Allow non-exclusive DAMON start/stop mm/damon/sysfs: Link DAMON to 'state' file read/write functions selftests/damon: Add a test for DAMON sysfs interface include/linux/damon.h | 2 +- mm/damon/Kconfig | 7 + mm/damon/Makefile | 1 + mm/damon/core.c | 22 +- mm/damon/dbgfs.c | 2 +- mm/damon/reclaim.c | 2 +- mm/damon/sysfs.c | 1258 ++++++++++++++++++++++++ tools/testing/selftests/damon/Makefile | 1 + tools/testing/selftests/damon/sysfs.sh | 200 ++++ 9 files changed, 1486 insertions(+), 9 deletions(-) create mode 100644 mm/damon/sysfs.c create mode 100755 tools/testing/selftests/damon/sysfs.sh