[PATCH 3/4] oom: take per file badness into account

[Christian König]

From: Christian König <christian.koenig at amd.com>

Try to make better decisions which process to kill based on
per file OOM badness.

Signed-off-by: Christian König <christian.koenig at amd.com>
Reviewed-by: Alex Deucher <alexander.deucher at amd.com>
---
 mm/oom_kill.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 2b665da..4bcb3f4 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -35,6 +35,7 @@
 #include <linux/freezer.h>
 #include <linux/ftrace.h>
 #include <linux/ratelimit.h>
+#include <linux/fdtable.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/oom.h>
@@ -138,6 +139,19 @@ static bool oom_unkillable_task(struct task_struct *p,
 }
 
 /**
+ * oom_file_badness - add per file badness
+ * @points: pointer to summed up badness points
+ * @file: tasks open file
+ * @n: file descriptor id (unused)
+ */
+static int oom_file_badness(const void *points, struct file *file, unsigned n)
+{
+	*((long*)points) += atomic_long_read(&file->f_oom_badness);
+
+	return 0;
+}
+
+/**
  * oom_badness - heuristic function to determine which candidate task to kill
  * @p: task struct of which task we should calculate
  * @totalpages: total present RAM allowed for page allocation
@@ -171,6 +185,12 @@ unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg,
 	 */
 	points = get_mm_rss(p->mm) + get_mm_counter(p->mm, MM_SWAPENTS) +
 		atomic_long_read(&p->mm->nr_ptes) + mm_nr_pmds(p->mm);
+
+	/*
+	 * Add how much memory a task uses in opened files, e.g. device drivers.
+	 */
+	iterate_fd(p->files, 0, oom_file_badness, &points);
+
 	task_unlock(p);
 
 	/*
-- 
1.9.1