From patchwork Fri Jun 10 19:44:27 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yosry Ahmed X-Patchwork-Id: 12878001 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 E188FC433EF for ; Fri, 10 Jun 2022 19:44:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347623AbiFJToo (ORCPT ); Fri, 10 Jun 2022 15:44:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44912 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343917AbiFJTon (ORCPT ); Fri, 10 Jun 2022 15:44:43 -0400 Received: from mail-pj1-x1049.google.com (mail-pj1-x1049.google.com [IPv6:2607:f8b0:4864:20::1049]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B79DE3631E for ; Fri, 10 Jun 2022 12:44:41 -0700 (PDT) Received: by mail-pj1-x1049.google.com with SMTP id c14-20020a17090a1d0e00b001e328238e7eso62978pjd.4 for ; Fri, 10 Jun 2022 12:44:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:message-id:mime-version:subject:from:to:cc; bh=i6zkq+SbTrXADRy8+ig+1J4qQLsOeKLI1rJct5wsC9M=; b=oENthMDx1DemDENCKb7+vR7A7KrZ7ow+cOkqgpT6ERoa9Z51W1sj50TrJ8NjWW1e7P WmwmpRLa7IBRpvSKKK3KUypFHi2UYXbl0mXpkeIz92R+yq1Fz7WLAs1pikLdRUzShb7K praWX/XjS3A+mYEZwW48swWq4dZ3WOkvu4+a3TCJCw7VCvhFP7xbEM458N5UQU23aDfK kWthEGQRt9h8V/8C+thO62LIRmy3vTEFjdRiW0h8/xgNU3DX5oa+r2NIvHypB0cPOhAb JymCgAsdgRzr4Dp5NWTjkV0Q13YtYxhwnRKyqajWXITueq4CrMS5Sc/KVlolYNq8nplF QVMg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=i6zkq+SbTrXADRy8+ig+1J4qQLsOeKLI1rJct5wsC9M=; b=z95EBevtpOg7l/xYWp/GUDzVcZdVVTmvqzQnv7mlxrWDMuEtJa5yRhBfLfsb1On0y7 h6HhkQyTs5yQt9+W7icuSstAdhrI4OcphwGuy3FL7OBylEiKnx8vBe8ueCKHzXND3yKq aATd8mDUUXjCewjqOrRj+1Oc9E7JUsnI2dnm3dA+AdXa7gqTv8w5+zLqRXKeBEUT7w6k ss8HDMiYZzPO2ATXWdcwd+oe79EHrB7q4x1qUw+guVb/1GWjMbxQ/NGQXnPTbtayNwjZ xJImw8aOUjX0C1YAZlP+xckj8I1470xyGuiBn26ZnOI9I7R9wQ48/XCoFaBk3x31hEuQ T5IQ== X-Gm-Message-State: AOAM530iFrHGpm/KVHphyZWfhzSqraXl36ZI1goe5unM0CVoUU9g/E/L vzDD8CUpvmpEdKuaXgEqLnhDnEefP8uXq6/Y X-Google-Smtp-Source: ABdhPJxtdO6pRShCr96FVJhsqRyi3L1gIlwPDweIzWvz3ftA8aV64mUawP4Nqp2M5P34aQSrYCK2YEWR/tPv4pIU X-Received: from yosry.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:2327]) (user=yosryahmed job=sendgmr) by 2002:a05:6a00:2341:b0:51c:6413:ab2e with SMTP id j1-20020a056a00234100b0051c6413ab2emr16265298pfj.63.1654890281125; Fri, 10 Jun 2022 12:44:41 -0700 (PDT) Date: Fri, 10 Jun 2022 19:44:27 +0000 Message-Id: <20220610194435.2268290-1-yosryahmed@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.36.1.476.g0c4daa206d-goog Subject: [PATCH bpf-next v2 0/8] bpf: rstat: cgroup hierarchical stats From: Yosry Ahmed To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Hao Luo , Tejun Heo , Zefan Li , Johannes Weiner , Shuah Khan , Michal Hocko Cc: Roman Gushchin , David Rientjes , Stanislav Fomichev , Greg Thelen , Shakeel Butt , linux-kernel@vger.kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, cgroups@vger.kernel.org, Yosry Ahmed Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net This patch series allows for using bpf to collect hierarchical cgroup stats efficiently by integrating with the rstat framework. The rstat framework provides an efficient way to collect cgroup stats percpu and propagate them through the cgroup hierarchy. The stats are exposed to userspace in textual form by reading files in bpffs, similar to cgroupfs stats by using a cgroup_iter program. cgroup_iter is a type of bpf_iter. It walks over cgroups in two modes: - walking a cgroup's descendants. - walking a cgroup's ancestors. When attaching cgroup_iter, one needs to set a cgroup to the iter_link created from attaching. This cgroup is passed as a file descriptor and serves as the starting point of the walk. For walking descendants, one can specify the order: either pre-order or post-order. For walking ancestors, the walk starts at the specified cgroup and ends at the root. One can also terminate the walk early by returning 1 from the iter program. Note that because walking cgroup hierarchy holds cgroup_mutex, the iter program is called with cgroup_mutex held. ** Background on rstat for stats collection ** (I am using a subscriber analogy that is not commonly used) The rstat framework maintains a tree of cgroups that have updates and which cpus have updates. A subscriber to the rstat framework maintains their own stats. The framework is used to tell the subscriber when and what to flush, for the most efficient stats propagation. The workflow is as follows: - When a subscriber updates a cgroup on a cpu, it informs the rstat framework by calling cgroup_rstat_updated(cgrp, cpu). - When a subscriber wants to read some stats for a cgroup, it asks the rstat framework to initiate a stats flush (propagation) by calling cgroup_rstat_flush(cgrp). - When the rstat framework initiates a flush, it makes callbacks to subscribers to aggregate stats on cpus that have updates, and propagate updates to their parent. Currently, the main subscribers to the rstat framework are cgroup subsystems (e.g. memory, block). This patch series allow bpf programs to become subscribers as well. Patches in this series are based off a patch in the mailing list which adds a new kfunc set for sleepable functions: "btf: Add a new kfunc set which allows to mark a function to be sleepable" [1]. Patches in this series are organized as follows: * Patch 1 enables the use of cgroup_get_from_file() in cgroup1. This is useful because it enables cgroup_iter to work with cgroup1, and allows the entire stat collection workflow to be cgroup1-compatible. * Patches 2-5 introduce cgroup_iter prog, and a selftest. * Patches 6-8 allow bpf programs to integrate with rstat by adding the necessary hook points and kfunc. A comprehensive selftest that demonstrates the entire workflow for using bpf and rstat to efficiently collect and output cgroup stats is added. v1 -> v2: - Redesign of cgroup_iter from v1, based on Alexei's idea [2]: - supports walking cgroup subtree. - supports walking ancestors of a cgroup. (Andrii) - supports terminating the walk early. - uses fd instead of cgroup_id as parameter for iter_link. Using fd is a convention in bpf. - gets cgroup's ref at attach time and deref at detach. - brought back cgroup1 support for cgroup_iter. - Squashed the patches adding the rstat flush hook points and kfuncs (Tejun). - Added a comment explaining why bpf_rstat_flush() needs to be weak (Tejun). - Updated the final selftest with the new cgroup_iter design. - Changed CHECKs in the selftest with ASSERTs (Yonghong, Andrii). - Removed empty line at the end of the selftest (Yonghong). - Renamed test files to cgroup_hierarchical_stats.c. - Reordered CGROUP_PATH params order to match struct declaration in the selftest (Michal). - Removed memory_subsys_enabled() and made sure memcg controller enablement checks make sense and are documented (Michal). RFC v2 -> v1: - Instead of introducing a new program type for rstat flushing, add an empty hook point, bpf_rstat_flush(), and use fentry bpf programs to attach to it and flush bpf stats. - Instead of using helpers, use kfuncs for rstat functions. - These changes simplify the patchset greatly, with minimal changes to uapi. RFC v1 -> RFC v2: - Instead of rstat flush programs attach to subsystems, they now attach to rstat (global flushers, not per-subsystem), based on discussions with Tejun. The first patch is entirely rewritten. - Pass cgroup pointers to rstat flushers instead of cgroup ids. This is much more flexibility and less likely to need a uapi update later. - rstat helpers are now only defined if CGROUP_CONFIG. - Most of the code is now only defined if CGROUP_CONFIG and CONFIG_BPF_SYSCALL. - Move rstat helper protos from bpf_base_func_proto() to tracing_prog_func_proto(). - rstat helpers argument (cgroup pointer) is now ARG_PTR_TO_BTF_ID, not ARG_ANYTHING. - Rewrote the selftest to use the cgroup helpers. - Dropped bpf_map_lookup_percpu_elem (already added by Feng). - Dropped patch to support cgroup v1 for cgroup_iter. - Dropped patch to define some cgroup_put() when !CONFIG_CGROUP. The code that calls it is no longer compiled when !CONFIG_CGROUP. cgroup_iter was originally introduced in a different patch series[3]. Hao and I agreed that it fits better as part of this series. RFC v1 of this patch series had the following changes from [3]: - Getting the cgroup's reference at the time at attaching, instead of at the time when iterating. (Yonghong) - Remove .init_seq_private and .fini_seq_private callbacks for cgroup_iter. They are not needed now. (Yonghong) [1] https://lore.kernel.org/bpf/20220421140740.459558-5-benjamin.tissoires@redhat.com/ [2] https://lore.kernel.org/bpf/20220520221919.jnqgv52k4ajlgzcl@MBP-98dd607d3435.dhcp.thefacebook.com/ [3] https://lore.kernel.org/lkml/20220225234339.2386398-9-haoluo@google.com/ Hao Luo (4): cgroup: Add cgroup_put() in !CONFIG_CGROUPS case bpf, iter: Fix the condition on p when calling stop. bpf: Introduce cgroup iter selftests/bpf: Test cgroup_iter. Yosry Ahmed (4): cgroup: enable cgroup_get_from_file() on cgroup1 cgroup: bpf: enable bpf programs to integrate with rstat selftests/bpf: extend cgroup helpers bpf: add a selftest for cgroup hierarchical stats collection include/linux/bpf.h | 8 + include/linux/cgroup.h | 3 + include/uapi/linux/bpf.h | 21 ++ kernel/bpf/Makefile | 2 +- kernel/bpf/bpf_iter.c | 5 + kernel/bpf/cgroup_iter.c | 235 ++++++++++++ kernel/cgroup/cgroup.c | 5 - kernel/cgroup/rstat.c | 46 +++ tools/include/uapi/linux/bpf.h | 21 ++ tools/testing/selftests/bpf/cgroup_helpers.c | 173 +++++++-- tools/testing/selftests/bpf/cgroup_helpers.h | 15 +- .../prog_tests/cgroup_hierarchical_stats.c | 351 ++++++++++++++++++ .../selftests/bpf/prog_tests/cgroup_iter.c | 190 ++++++++++ tools/testing/selftests/bpf/progs/bpf_iter.h | 7 + .../bpf/progs/cgroup_hierarchical_stats.c | 234 ++++++++++++ .../testing/selftests/bpf/progs/cgroup_iter.c | 39 ++ 16 files changed, 1303 insertions(+), 52 deletions(-) create mode 100644 kernel/bpf/cgroup_iter.c create mode 100644 tools/testing/selftests/bpf/prog_tests/cgroup_hierarchical_stats.c create mode 100644 tools/testing/selftests/bpf/prog_tests/cgroup_iter.c create mode 100644 tools/testing/selftests/bpf/progs/cgroup_hierarchical_stats.c create mode 100644 tools/testing/selftests/bpf/progs/cgroup_iter.c