linux-kernel - [PATCH] mm/oom: Add killed process selection information

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Message-Id: <20190815060604.3675-1-echron@arista.com>
Date:   Wed, 14 Aug 2019 23:06:04 -0700
From:   Edward Chron <echron@...sta.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Michal Hocko <mhocko@...e.com>, Roman Gushchin <guro@...com>,
        Johannes Weiner <hannes@...xchg.org>,
        David Rientjes <rientjes@...gle.com>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Shakeel Butt <shakeelb@...gle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, colona@...sta.com,
        Edward Chron <echron@...sta.com>
Subject: [PATCH] mm/oom: Add killed process selection information

For an OOM event: print oom_score_adj value for the OOM Killed process
to document what the oom score adjust value was at the time the process
at the time of the OOM event. The value can be set by the user and it
effects the resulting oom_score so useful to document this value.

Sample message output:
Aug 14 23:00:02 testserver kernel: Out of memory: Killed process 2692
 (oomprocs) total-vm:1056800kB, anon-rss:1052760kB, file-rss:4kB,i
 shmem-rss:0kB oom_score_adj:1000

Signed-off-by: Edward Chron <echron@...sta.com>
---
 mm/oom_kill.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index eda2e2a0bdc6..6b1674cac377 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -858,6 +858,7 @@ static void __oom_kill_process(struct task_struct *victim, const char *message)
 	struct task_struct *p;
 	struct mm_struct *mm;
 	bool can_oom_reap = true;
+	long adj;
 
 	p = find_lock_task_mm(victim);
 	if (!p) {
@@ -877,6 +878,8 @@ static void __oom_kill_process(struct task_struct *victim, const char *message)
 	count_vm_event(OOM_KILL);
 	memcg_memory_event_mm(mm, MEMCG_OOM_KILL);
 
+	adj = (long)victim->signal->oom_score_adj;
+
 	/*
 	 * We should send SIGKILL before granting access to memory reserves
 	 * in order to prevent the OOM victim from depleting the memory
@@ -884,12 +887,12 @@ static void __oom_kill_process(struct task_struct *victim, const char *message)
 	 */
 	do_send_sig_info(SIGKILL, SEND_SIG_PRIV, victim, PIDTYPE_TGID);
 	mark_oom_victim(victim);
-	pr_err("%s: Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
+	pr_err("%s: Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB oom_score_adj:%ld\n",
 		message, task_pid_nr(victim), victim->comm,
 		K(victim->mm->total_vm),
 		K(get_mm_counter(victim->mm, MM_ANONPAGES)),
 		K(get_mm_counter(victim->mm, MM_FILEPAGES)),
-		K(get_mm_counter(victim->mm, MM_SHMEMPAGES)));
+		K(get_mm_counter(victim->mm, MM_SHMEMPAGES)), adj);
 	task_unlock(victim);
 
 	/*
-- 
2.20.1