From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: [PATCH REPOST 2/2] cgroup, perf_event: make perf_event controller work on cgroup2 hierarchy Date: Sun, 29 Jan 2017 14:35:20 -0500 Message-ID: <20170129193520.GA18336@mtj.duckdns.org> References: <1456351975-1899-1-git-send-email-tj@kernel.org> <1456351975-1899-3-git-send-email-tj@kernel.org> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=2luogTptRqcgql2je1HgNu8xAyfRenUHvDEXWje3Yy4=; b=pIeLJJcdANjJfxlOeHpnYrEmESHxm0PbR0XznweQPbiLMWeV85OMuvdFkByCuTKy1B JsJD+jJACqPAsDkW4vSSRUl8XhAY5sQ2sn8E6QIfhacJSTfJGr1C+x9rSAxV4qztb0pA dSSeXmGh1vQx5GmtXfEYY2xsjOHKMj05h2gd0cGHgZealh+tEoCzMFWRfo3kT69gNyqL p6EwtIkbsxnJcAlYrw91sGDQB6dsEuVd5DhzcbJisSsoA+lI/bqe6luzgG69dIP7TP7y h6id2VBSqNyZnx1/yMugRml8/JPyQhxi/s3+dAb7124xtZPdaLesvuwmzB45TaE1B/fc WNgQ== Content-Disposition: inline In-Reply-To: <1456351975-1899-3-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org, hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org, a.p.zijlstra-/NLkJaSkS4VmR6Xm/wNWPw@public.gmane.org, mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, acme-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kernel-team-b10kYP2dOMg@public.gmane.org perf_event is a utility controller whose primary role is identifying cgroup membership to filter perf events; however, because it also tracks some per-css state, it can't be replaced by pure cgroup membership test. Mark the controller as implicitly enabled on the default hierarchy so that perf events can always be filtered based on cgroup v2 path as long as the controller is not mounted on a legacy hierarchy. "perf record" is updated accordingly so that it searches for both v1 and v2 hierarchies. A v1 hierarchy is used if perf_event is mounted on it; otherwise, it uses the v2 hierarchy. v2: Doc updated to reflect more flexible rebinding behavior. Signed-off-by: Tejun Heo Acked-by: Peter Zijlstra Cc: Ingo Molnar Cc: Arnaldo Carvalho de Melo --- Hello, This was posted months ago and acked by Peter. I thought it was applied but apparently wasn't. Peter asked Arnaldo whether the userspace part looked which didn't get replied and that probably was how it slipped through the crack. Peter, Arnanldo, how should we proceed? Should I route this through the cgroup tree? Thanks. Documentation/cgroup-v2.txt | 12 ++++++++++++ kernel/events/core.c | 6 ++++++ tools/perf/util/cgroup.c | 26 +++++++++++++++++++------- 3 files changed, 37 insertions(+), 7 deletions(-) --- a/Documentation/cgroup-v2.txt +++ b/Documentation/cgroup-v2.txt @@ -49,6 +49,8 @@ CONTENTS 5-3-2. Writeback 5-4. PID 5-4-1. PID Interface Files + 5-5. Misc + 5-5-1. perf_event 6. Namespace 6-1. Basics 6-2. The Root and Views @@ -1160,6 +1162,16 @@ through fork() or clone(). These will re of a new process would cause a cgroup policy to be violated. +5-5. Misc + +5-5-1. perf_event + +perf_event controller, if not mounted on a legacy hierarchy, is +automatically enabled on the v2 hierarchy so that perf events can +always be filtered by cgroup v2 path. The controller can still be +moved to a legacy hierarchy after v2 hierarchy is populated. + + 6. Namespace 6-1. Basics --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -10792,5 +10792,11 @@ struct cgroup_subsys perf_event_cgrp_sub .css_alloc = perf_cgroup_css_alloc, .css_free = perf_cgroup_css_free, .attach = perf_cgroup_attach, + /* + * Implicitly enable on dfl hierarchy so that perf events can + * always be filtered by cgroup2 path as long as perf_event + * controller is not mounted on a legacy hierarchy. + */ + .implicit_on_dfl = true, }; #endif /* CONFIG_CGROUP_PERF */ --- a/tools/perf/util/cgroup.c +++ b/tools/perf/util/cgroup.c @@ -12,8 +12,8 @@ cgroupfs_find_mountpoint(char *buf, size { FILE *fp; char mountpoint[PATH_MAX + 1], tokens[PATH_MAX + 1], type[PATH_MAX + 1]; + char path_v1[PATH_MAX + 1], path_v2[PATH_MAX + 2], *path; char *token, *saved_ptr = NULL; - int found = 0; fp = fopen("/proc/mounts", "r"); if (!fp) @@ -24,31 +24,43 @@ cgroupfs_find_mountpoint(char *buf, size * and inspect every cgroupfs mount point to find one that has * perf_event subsystem */ + path_v1[0] = '\0'; + path_v2[0] = '\0'; + while (fscanf(fp, "%*s %"STR(PATH_MAX)"s %"STR(PATH_MAX)"s %" STR(PATH_MAX)"s %*d %*d\n", mountpoint, type, tokens) == 3) { - if (!strcmp(type, "cgroup")) { + if (!path_v1[0] && !strcmp(type, "cgroup")) { token = strtok_r(tokens, ",", &saved_ptr); while (token != NULL) { if (!strcmp(token, "perf_event")) { - found = 1; + strcpy(path_v1, mountpoint); break; } token = strtok_r(NULL, ",", &saved_ptr); } } - if (found) + + if (!path_v2[0] && !strcmp(type, "cgroup2")) + strcpy(path_v2, mountpoint); + + if (path_v1[0] && path_v2[0]) break; } fclose(fp); - if (!found) + + if (path_v1[0]) + path = path_v1; + else if (path_v2[0]) + path = path_v2; + else return -1; - if (strlen(mountpoint) < maxlen) { - strcpy(buf, mountpoint); + if (strlen(path) < maxlen) { + strcpy(buf, path); return 0; } return -1;