tracepoint: add tracepoints for debugging oom_score_adj

oom_score_adj is used for guarding processes from OOM-Killer.  One of
problem is that it's inherited at fork().  When a daemon set oom_score_adj
and make children, it's hard to know where the value is set.

This patch adds some tracepoints useful for debugging. This patch adds
3 trace points.
  - creating new task
  - renaming a task (exec)
  - set oom_score_adj

To debug, users need to enable some trace pointer. Maybe filtering is useful as

# EVENT=/sys/kernel/debug/tracing/events/task/
# echo "oom_score_adj != 0" > $EVENT/task_newtask/filter
# echo "oom_score_adj != 0" > $EVENT/task_rename/filter
# echo 1 > $EVENT/enable
# EVENT=/sys/kernel/debug/tracing/events/oom/
# echo 1 > $EVENT/enable

output will be like this.
# grep oom /sys/kernel/debug/tracing/trace
bash-7699  [007] d..3  5140.744510: oom_score_adj_update: pid=7699 comm=bash oom_score_adj=-1000
bash-7699  [007] ...1  5151.818022: task_newtask: pid=7729 comm=bash clone_flags=1200011 oom_score_adj=-1000
ls-7729  [003] ...2  5151.818504: task_rename: pid=7729 oldcomm=bash newcomm=ls oom_score_adj=-1000
bash-7699  [002] ...1  5175.701468: task_newtask: pid=7730 comm=bash clone_flags=1200011 oom_score_adj=-1000
grep-7730  [007] ...2  5175.701993: task_rename: pid=7730 oldcomm=bash newcomm=grep oom_score_adj=-1000

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 94 insertions, 0 deletions

diff --git a/include/trace/events/oom.h b/include/trace/events/oom.h
new file mode 100644
index 000000000000..dd4ba3b92002
--- /dev/null
+++ b/include/trace/events/oom.h
@@ -0,0 +1,33 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM oom
+
+#if !defined(_TRACE_OOM_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_OOM_H
+#include <linux/tracepoint.h>
+
+TRACE_EVENT(oom_score_adj_update,
+
+        TP_PROTO(struct task_struct *task),
+
+        TP_ARGS(task),
+
+        TP_STRUCT__entry(
+                __field(        pid_t,  pid)
+                __array(        char,   comm,   TASK_COMM_LEN )
+                __field(         int,   oom_score_adj)
+        ),
+
+        TP_fast_assign(
+                __entry->pid = task->pid;
+                memcpy(__entry->comm, task->comm, TASK_COMM_LEN);
+                __entry->oom_score_adj = task->signal->oom_score_adj;
+        ),
+
+        TP_printk("pid=%d comm=%s oom_score_adj=%d",
+                __entry->pid, __entry->comm, __entry->oom_score_adj)
+);
+
+#endif
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
diff --git a/include/trace/events/task.h b/include/trace/events/task.h
new file mode 100644
index 000000000000..b53add02e929
--- /dev/null
+++ b/include/trace/events/task.h
@@ -0,0 +1,61 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM task
+
+#if !defined(_TRACE_TASK_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_TASK_H
+#include <linux/tracepoint.h>
+
+TRACE_EVENT(task_newtask,
+
+        TP_PROTO(struct task_struct *task, unsigned long clone_flags),
+
+        TP_ARGS(task, clone_flags),
+
+        TP_STRUCT__entry(
+                __field(        pid_t,  pid)
+                __array(        char,   comm, TASK_COMM_LEN)
+                __field( unsigned long, clone_flags)
+                __field(        int,    oom_score_adj)
+        ),
+
+        TP_fast_assign(
+                __entry->pid = task->pid;
+                memcpy(__entry->comm, task->comm, TASK_COMM_LEN);
+                __entry->clone_flags = clone_flags;
+                __entry->oom_score_adj = task->signal->oom_score_adj;
+        ),
+
+        TP_printk("pid=%d comm=%s clone_flags=%lx oom_score_adj=%d",
+                __entry->pid, __entry->comm,
+                __entry->clone_flags, __entry->oom_score_adj)
+);
+
+TRACE_EVENT(task_rename,
+
+        TP_PROTO(struct task_struct *task, char *comm),
+
+        TP_ARGS(task, comm),
+
+        TP_STRUCT__entry(
+                __field(        pid_t,  pid)
+                __array(        char, oldcomm,  TASK_COMM_LEN)
+                __array(        char, newcomm,  TASK_COMM_LEN)
+                __field(        int, oom_score_adj)
+        ),
+
+        TP_fast_assign(
+                __entry->pid = task->pid;
+                memcpy(entry->oldcomm, task->comm, TASK_COMM_LEN);
+                memcpy(entry->newcomm, comm, TASK_COMM_LEN);
+                __entry->oom_score_adj = task->signal->oom_score_adj;
+        ),
+
+        TP_printk("pid=%d oldcomm=%s newcomm=%s oom_score_adj=%d",
+                __entry->pid, __entry->oldcomm,
+                __entry->newcomm, __entry->oom_score_adj)
+);
+
+#endif
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>