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Subject[PATCH v10 8/9] cgroup: add tracing points for cgroup v2 freezer
Date
Add cgroup:cgroup_freeze and cgroup:cgroup_unfreeze events,
which are using the existing cgroup tracing infrastructure.

Add the cgroup_event event class, which is similar to the cgroup
class, but contains an additional integer field to store a new
value (the level field is dropped).

Also add two tracing events: cgroup_notify_populated and
cgroup_notify_frozen, which are raised in a generic way using
the TRACE_CGROUP_PATH() macro.

This allows to trace cgroup state transitions and is generally
helpful for debugging the cgroup freezer code.

Signed-off-by: Roman Gushchin <guro@fb.com>
---
include/trace/events/cgroup.h | 55 +++++++++++++++++++++++++++++++++++
kernel/cgroup/cgroup.c | 2 ++
kernel/cgroup/freezer.c | 15 +++++++++-
3 files changed, 71 insertions(+), 1 deletion(-)

diff --git a/include/trace/events/cgroup.h b/include/trace/events/cgroup.h
index a401ff5e7847..a566cc521476 100644
--- a/include/trace/events/cgroup.h
+++ b/include/trace/events/cgroup.h
@@ -103,6 +103,20 @@ DEFINE_EVENT(cgroup, cgroup_rename,
TP_ARGS(cgrp, path)
);

+DEFINE_EVENT(cgroup, cgroup_freeze,
+
+ TP_PROTO(struct cgroup *cgrp, const char *path),
+
+ TP_ARGS(cgrp, path)
+);
+
+DEFINE_EVENT(cgroup, cgroup_unfreeze,
+
+ TP_PROTO(struct cgroup *cgrp, const char *path),
+
+ TP_ARGS(cgrp, path)
+);
+
DECLARE_EVENT_CLASS(cgroup_migrate,

TP_PROTO(struct cgroup *dst_cgrp, const char *path,
@@ -149,6 +163,47 @@ DEFINE_EVENT(cgroup_migrate, cgroup_transfer_tasks,
TP_ARGS(dst_cgrp, path, task, threadgroup)
);

+DECLARE_EVENT_CLASS(cgroup_event,
+
+ TP_PROTO(struct cgroup *cgrp, const char *path, int val),
+
+ TP_ARGS(cgrp, path, val),
+
+ TP_STRUCT__entry(
+ __field( int, root )
+ __field( int, id )
+ __field( int, level )
+ __string( path, path )
+ __field( int, val )
+ ),
+
+ TP_fast_assign(
+ __entry->root = cgrp->root->hierarchy_id;
+ __entry->id = cgrp->id;
+ __entry->level = cgrp->level;
+ __assign_str(path, path);
+ __entry->val = val;
+ ),
+
+ TP_printk("root=%d id=%d level=%d path=%s val=%d",
+ __entry->root, __entry->id, __entry->level, __get_str(path),
+ __entry->val)
+);
+
+DEFINE_EVENT(cgroup_event, cgroup_notify_populated,
+
+ TP_PROTO(struct cgroup *cgrp, const char *path, int val),
+
+ TP_ARGS(cgrp, path, val)
+);
+
+DEFINE_EVENT(cgroup_event, cgroup_notify_frozen,
+
+ TP_PROTO(struct cgroup *cgrp, const char *path, int val),
+
+ TP_ARGS(cgrp, path, val)
+);
+
#endif /* _TRACE_CGROUP_H */

/* This part must be outside protection */
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 6895464b54c6..57edcf398d71 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -816,6 +816,8 @@ static void cgroup_update_populated(struct cgroup *cgrp, bool populated)
break;

cgroup1_check_for_release(cgrp);
+ TRACE_CGROUP_PATH(notify_populated, cgrp,
+ cgroup_is_populated(cgrp));
cgroup_file_notify(&cgrp->events_file);

child = cgrp;
diff --git a/kernel/cgroup/freezer.c b/kernel/cgroup/freezer.c
index 9d8cda478fc9..3bfbb3c8baf3 100644
--- a/kernel/cgroup/freezer.c
+++ b/kernel/cgroup/freezer.c
@@ -6,6 +6,8 @@

#include "cgroup-internal.h"

+#include <trace/events/cgroup.h>
+
/*
* Propagate the cgroup frozen state upwards by the cgroup tree.
*/
@@ -28,6 +30,7 @@ static void cgroup_propagate_frozen(struct cgroup *cgrp, bool frozen)
cgrp->nr_descendants) {
set_bit(CGRP_FROZEN, &cgrp->flags);
cgroup_file_notify(&cgrp->events_file);
+ TRACE_CGROUP_PATH(notify_frozen, cgrp, 1);
desc++;
}
} else {
@@ -35,6 +38,7 @@ static void cgroup_propagate_frozen(struct cgroup *cgrp, bool frozen)
if (test_bit(CGRP_FROZEN, &cgrp->flags)) {
clear_bit(CGRP_FROZEN, &cgrp->flags);
cgroup_file_notify(&cgrp->events_file);
+ TRACE_CGROUP_PATH(notify_frozen, cgrp, 0);
desc++;
}
}
@@ -73,6 +77,7 @@ void cgroup_update_frozen(struct cgroup *cgrp)
clear_bit(CGRP_FROZEN, &cgrp->flags);
}
cgroup_file_notify(&cgrp->events_file);
+ TRACE_CGROUP_PATH(notify_frozen, cgrp, frozen);

/* Update the state of ancestor cgroups. */
cgroup_propagate_frozen(cgrp, frozen);
@@ -189,6 +194,11 @@ static void cgroup_do_freeze(struct cgroup *cgrp, bool freeze)
clear_bit(CGRP_FREEZE, &cgrp->flags);
spin_unlock_irq(&css_set_lock);

+ if (freeze)
+ TRACE_CGROUP_PATH(freeze, cgrp);
+ else
+ TRACE_CGROUP_PATH(unfreeze, cgrp);
+
css_task_iter_start(&cgrp->self, 0, &it);
while ((task = css_task_iter_next(&it))) {
/*
@@ -312,6 +322,9 @@ void cgroup_freeze(struct cgroup *cgrp, bool freeze)
* In both cases it's better to notify a user, that there is
* nothing to wait for.
*/
- if (!applied)
+ if (!applied) {
+ TRACE_CGROUP_PATH(notify_frozen, cgrp,
+ test_bit(CGRP_FROZEN, &cgrp->flags));
cgroup_file_notify(&cgrp->events_file);
+ }
}
--
2.20.1
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