[PATCH v2] mm: Update mark_victim tracepoints fields

[Carlos Galo]

The current implementation of the mark_victim tracepoint provides only
the process ID (pid) of the victim process. This limitation poses
challenges for userspace tools that need additional information
about the OOM victim. The association between pid and the additional
data may be lost after the kill, making it difficult for userspace to
correlate the OOM event with the specific process.

In order to mitigate this limitation, add the following fields:

- UID
   In Android each installed application has a unique UID. Including
   the `uid` assists in correlating OOM events with specific apps.

- Process Name (comm)
   Enables identification of the affected process.

- OOM Score
   Allows userspace to get additional insights of the relative kill
   priority of the OOM victim.

Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Signed-off-by: Carlos Galo <carlosgalo@xxxxxxxxxx>
---
v2: Fixed build error. Added missing comma when printing `__entry->uid`.

 include/trace/events/oom.h | 19 +++++++++++++++----
 mm/oom_kill.c              |  6 +++++-
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/include/trace/events/oom.h b/include/trace/events/oom.h
index 26a11e4a2c36..fb8a5d1b8a0a 100644
--- a/include/trace/events/oom.h
+++ b/include/trace/events/oom.h
@@ -72,19 +72,30 @@ TRACE_EVENT(reclaim_retry_zone,
 );
 
 TRACE_EVENT(mark_victim,
-	TP_PROTO(int pid),
+	TP_PROTO(struct task_struct *task, uid_t uid),
 
-	TP_ARGS(pid),
+	TP_ARGS(task, uid),
 
 	TP_STRUCT__entry(
 		__field(int, pid)
+		__field(uid_t, uid)
+		__string(comm, task->comm)
+		__field(short, oom_score_adj)
 	),
 
 	TP_fast_assign(
-		__entry->pid = pid;
+		__entry->pid = task->pid;
+		__entry->uid = uid;
+		__assign_str(comm, task->comm);
+		__entry->oom_score_adj = task->signal->oom_score_adj;
 	),
 
-	TP_printk("pid=%d", __entry->pid)
+	TP_printk("pid=%d uid=%u comm=%s oom_score_adj=%hd",
+		__entry->pid,
+		__entry->uid,
+		__get_str(comm),
+		__entry->oom_score_adj
+	)
 );
 
 TRACE_EVENT(wake_reaper,
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 9e6071fde34a..0698c00c5da6 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -44,6 +44,7 @@
 #include <linux/kthread.h>
 #include <linux/init.h>
 #include <linux/mmu_notifier.h>
+#include <linux/cred.h>
 
 #include <asm/tlb.h>
 #include "internal.h"
@@ -753,6 +754,7 @@ static inline void queue_oom_reaper(struct task_struct *tsk)
  */
 static void mark_oom_victim(struct task_struct *tsk)
 {
+	const struct cred *cred;
 	struct mm_struct *mm = tsk->mm;
 
 	WARN_ON(oom_killer_disabled);
@@ -772,7 +774,9 @@ static void mark_oom_victim(struct task_struct *tsk)
 	 */
 	__thaw_task(tsk);
 	atomic_inc(&oom_victims);
-	trace_mark_victim(tsk->pid);
+	cred = get_task_cred(tsk);
+	trace_mark_victim(tsk, cred->uid.val);
+	put_cred(cred);
 }
 
 /**

base-commit: 0dd3ee31125508cd67f7e7172247f05b7fd1753a
-- 
2.43.0.275.g3460e3d667-goog