From 968ebff1efde6948564308836ecf1ef57de4e106 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Sun, 29 Jan 2017 14:35:20 -0500 Subject: [PATCH] cgroup, perf_event: make perf_event controller work on cgroup2 hierarchy 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 --- Documentation/cgroup-v2.txt | 12 ++++++++++++ kernel/events/core.c | 6 ++++++ tools/perf/util/cgroup.c | 26 +++++++++++++++++++------- 3 files changed, 37 insertions(+), 7 deletions(-) diff --git a/Documentation/cgroup-v2.txt b/Documentation/cgroup-v2.txt index f6f54107fb4d..227ce4883720 100644 --- 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 return -EAGAIN if the creation 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 diff --git a/kernel/events/core.c b/kernel/events/core.c index ab15509fab8c..d72128dce1e0 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -10792,5 +10792,11 @@ struct cgroup_subsys perf_event_cgrp_subsys = { .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 */ diff --git a/tools/perf/util/cgroup.c b/tools/perf/util/cgroup.c index 8fdee24725a7..eafbf11442b2 100644 --- a/tools/perf/util/cgroup.c +++ b/tools/perf/util/cgroup.c @@ -12,8 +12,8 @@ cgroupfs_find_mountpoint(char *buf, size_t maxlen) { 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_t maxlen) * 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;