From patchwork Tue Jun 4 02:05:49 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yuanchu Xie X-Patchwork-Id: 13684566 Received: from mail-yw1-f202.google.com (mail-yw1-f202.google.com [209.85.128.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 43E36140399 for ; Tue, 4 Jun 2024 02:06:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717466784; cv=none; b=I3FDOU0kjOqo2yJwom6qvg6NNE5HZjtJ3ZftcLT97WBHp/Ol3K7D6EToRaVY9ghQEBZ9u+9YA9c+B1aY+yS/2TFDuwt8MmTEr97q9gN8Zej7/cc3ODGePqG9ProtIVeZwgGkWuNKSBjiK5GZJRYCiZKP9e5Brij5kEGi8zAzL8E= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717466784; c=relaxed/simple; bh=eASpyk4WWK4m1u5bAgzdZmzHoLxlNRCkiIkqJ+AFaTw=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=AOlUGT6XNnvICm3YvXFQ93bGx7ULfkbfWIuQwkqItdwYt1nZpCMaevDdBhQYMFT0xxSISQaqlcB8yy/EuqR4Vp/Cs0/4fzFFF8vkM0fqxb3YUDMV2wB+cnbNTz1f2FfLNU1c7zZ0SJZCsDV3zUoVC09vcjc0v9onB4azlb5lpuo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--yuanchu.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=kw3CUsG4; arc=none smtp.client-ip=209.85.128.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--yuanchu.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="kw3CUsG4" Received: by mail-yw1-f202.google.com with SMTP id 00721157ae682-62a3dec382eso54944257b3.1 for ; Mon, 03 Jun 2024 19:06:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1717466782; x=1718071582; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=TnO0wJpr9VrNuJfB7YNxreIL5h7wQch0G6mtECTuPNI=; b=kw3CUsG4HuXRbBfwPxIlmqbR59+zdoruCRpZfL487nlZ/KeYrxAz5IYal2lceH7KcQ M090USlbcJr0vsXC4S19u/7Wl64ULN/7p+VrkpqJB2xukoqq/ZTtsK2BND/MKg5tcRP4 g68Zq1Lyl0xQ8Qyos4iFJUsv2uRnYVQV77jpfMKFYy8gHKVKh+k99f9oDe9eijg5ov1r GiveBNjP+eolSf94p441u8j3HDuZO8hjKV63kEie0Og9IeVVt7JVw1FbSj+Luv6/vNz4 49+OPKcDmrWbAf9Nn7Mm+iKp8S/jQisMIqWGJekmOVrt92iCG9X1IkSqj0yC5GpD1vVM 1Sxg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1717466782; x=1718071582; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=TnO0wJpr9VrNuJfB7YNxreIL5h7wQch0G6mtECTuPNI=; b=KjuJRIlII+6xQFYDDBN6iBZ6Yy1iSBvtf7yenuk7ZYd6ylmbBIKffMwNzWidWTmJuF alXFCG/Z8h16P9slca2M6e0DcSyto12hBVLOIxvqug8gjgVhx1Vu1SiscYISkTf4ekxK uR4e5d8LCb5a+/FR6DNIJRSH5zhbS2TAgo0xQmMeIZcqkSiVJ5oEAyczp7HnXMBdh7Yf XOgTPIuDB5oGF3KLXYJN5bC+OWgab1hhHJa+e9PwOT0LeFgGE/Ez7+yjT25KdiTMYSvV 60Vlvf6YAMQahpusYHVbEpbT4VC7B/YJypmVLg9TPzshP6w5UIGfGAb6B9uUnjhALk80 AQjA== X-Forwarded-Encrypted: i=1; AJvYcCV6noyIs3MxP5/uYrBSJBAgOC06d8181pFkuAc9TsAd3MwnsuitvARteAB//s1mOYiPz77yhJDynBb0GgO+cDaM1bocbNfhHKsrv9H2Blw6 X-Gm-Message-State: AOJu0YzP3jFPet5rSkuLSqDyp/4ehfuTXT9Bof1W4tdYRcroUxbWQQX0 tKrTbx97E3+imbQrUzC9K7B7bg0F3OBZty6ITy6iy3DNImnYfiRtsZxIT5EtO5dOPPC/8TirChe PQqIgbA== X-Google-Smtp-Source: AGHT+IGZTKhErP0mteEdLmLII+zOO1bIGHOtdpRtyYGuauHmWRG/AEKax0/K3QpTHO4KkINtPULvAXTKU6Gn X-Received: from yuanchu-desktop.svl.corp.google.com ([2620:15c:2a3:200:367f:7387:3dd2:73f1]) (user=yuanchu job=sendgmr) by 2002:a81:c906:0:b0:618:9348:6b92 with SMTP id 00721157ae682-62cabc4cd34mr3112857b3.1.1717466782241; Mon, 03 Jun 2024 19:06:22 -0700 (PDT) Date: Mon, 3 Jun 2024 19:05:49 -0700 In-Reply-To: <20240604020549.1017540-1-yuanchu@google.com> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240604020549.1017540-1-yuanchu@google.com> X-Mailer: git-send-email 2.45.1.467.gbab1589fc0-goog Message-ID: <20240604020549.1017540-9-yuanchu@google.com> Subject: [PATCH v2 8/8] Docs/admin-guide/mm/workingset_report: document sysfs and memcg interfaces From: Yuanchu Xie To: David Hildenbrand , "Aneesh Kumar K.V" , Khalid Aziz , Henry Huang , Yu Zhao , Dan Williams , Gregory Price , Huang Ying , Muhammad Usama Anjum Cc: Kalesh Singh , Wei Xu , David Rientjes , Greg Kroah-Hartman , "Rafael J. Wysocki" , Andrew Morton , Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Shuah Khan , Yosry Ahmed , Matthew Wilcox , Sudarshan Rajagopalan , Kairui Song , "Michael S. Tsirkin" , Vasily Averin , Nhat Pham , Miaohe Lin , Qi Zheng , Abel Wu , "Vishal Moola (Oracle)" , Kefeng Wang , Yuanchu Xie , linux-kernel@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kselftest@vger.kernel.org Add workingset reporting documentation for better discoverability of its sysfs and memcg interfaces. Also document the required kernel config to enable workingset reporting. Signed-off-by: Yuanchu Xie --- Documentation/admin-guide/mm/index.rst | 1 + .../admin-guide/mm/workingset_report.rst | 105 ++++++++++++++++++ 2 files changed, 106 insertions(+) create mode 100644 Documentation/admin-guide/mm/workingset_report.rst diff --git a/Documentation/admin-guide/mm/index.rst b/Documentation/admin-guide/mm/index.rst index 1f883abf3f00..fba987de8997 100644 --- a/Documentation/admin-guide/mm/index.rst +++ b/Documentation/admin-guide/mm/index.rst @@ -41,4 +41,5 @@ the Linux memory management. swap_numa transhuge userfaultfd + workingset_report zswap diff --git a/Documentation/admin-guide/mm/workingset_report.rst b/Documentation/admin-guide/mm/workingset_report.rst new file mode 100644 index 000000000000..f455ae93b30e --- /dev/null +++ b/Documentation/admin-guide/mm/workingset_report.rst @@ -0,0 +1,105 @@ +.. SPDX-License-Identifier: GPL-2.0 + +================= +Workingset Report +================= +Workingset report provides a view of memory coldness in user-defined +time intervals, i.e. X bytes are Y milliseconds cold. It breaks down +the user pages in the system per-NUMA node, per-memcg, for both +anonymous and file pages into histograms that look like: +:: + + 1000 anon=137368 file=24530 + 20000 anon=34342 file=0 + 30000 anon=353232 file=333608 + 40000 anon=407198 file=206052 + 9223372036854775807 anon=4925624 file=892892 + +The workingset reports can be used to drive proactive reclaim, by +identifying the number of cold bytes in a memcg, then writing to +``memory.reclaim``. + +Quick start +=========== +Build the kernel with the following configurations. The report relies +on Multi-gen LRU for page coldness. + +* ``CONFIG_LRU_GEN=y`` +* ``CONFIG_LRU_GEN_ENABLED=y`` +* ``CONFIG_WORKINGSET_REPORT=y`` + +Optionally, the aging kernel daemon can be enabled with the following +configuration. +* ``CONFIG_LRU_GEN_ENABLED=y`` + +Sysfs interfaces +================ +``/sys/devices/system/node/nodeX/page_age`` provides a per-node page +age histogram, showing an aggregate of the node's lruvecs. +Reading this file causes a hierarchical aging of all lruvecs, scanning +pages and creates a new Multi-gen LRU generation in each lruvec. +For example: +:: + + 1000 anon=0 file=0 + 2000 anon=0 file=0 + 100000 anon=5533696 file=5566464 + 18446744073709551615 anon=0 file=0 + +``/sys/devices/system/node/nodeX/page_age_interval`` is a comma +separated list of time in milliseconds that configures what the page +age histogram uses for aggregation. For the above histogram, +the intervals are: +:: + 1000,2000,100000 + +``/sys/devices/system/node/nodeX/workingset_report/refresh_interval`` +defines the amount of time the report is valid for in milliseconds. +When a report is still valid, reading the ``page_age`` file shows +the existing valid report, instead of generating a new one. + +``/sys/devices/system/node/nodeX/workingset_report/report_threshold`` +specifies how often the userspace agent can be notified for node +memory pressure, in milliseconds. When a node reaches its low +watermarks and wakes up kswapd, programs waiting on ``page_age`` are +woken up so they can read the histogram and make policy decisions. + +Memcg interface +=============== +While ``page_age_interval`` is defined per-node in sysfs. ``page_age``, +``refresh_interval`` and ``report_threshold`` are available per-memcg. + +``/sys/fs/cgroup/.../memory.workingset.page_age`` +The memcg equivalent of the sysfs workingset page age histogram, +breaks down the workingset of this memcg and its children into +page age intervals. Each node is prefixed with a node header and +a newline. Non-proactive direct reclaim on this memcg can also +wake up userspace agents that are waiting on this file. +e.g. +:: + + N0 + 1000 anon=0 file=0 + 2000 anon=0 file=0 + 3000 anon=0 file=0 + 4000 anon=0 file=0 + 5000 anon=0 file=0 + 18446744073709551615 anon=0 file=0 + +``/sys/fs/cgroup/.../memory.workingset.refresh_interval`` +The memcg equivalent of the sysfs refresh interval. A per-node +number of how much time a page age histogram is valid for, in +milliseconds. +e.g. +:: + + echo N0=2000 > memory.workingset.refresh_interval + +``/sys/fs/cgroup/.../memory.workingset.report_threshold`` +The memcg equivalent of the sysfs report threshold. A per-node +number of how often userspace agent waiting on the page age +histogram can be woken up, in milliseconds. +e.g. +:: + + echo N0=1000 > memory.workingset.report_threshold