path: root/Documentation
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authorTejun Heo <>2017-01-29 14:35:20 -0500
committerTejun Heo <>2017-02-02 13:47:02 -0500
commit968ebff1efde6948564308836ecf1ef57de4e106 (patch)
tree0906d6efba1df934030a1356491c2899334375e3 /Documentation
parentb807421a720ff00bc31774d254f51313f4a7656b (diff)
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 <>
Diffstat (limited to 'Documentation')
1 files changed, 12 insertions, 0 deletions
diff --git a/Documentation/cgroup-v2.txt b/Documentation/cgroup-v2.txt
index f6f5410..227ce48 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