[PATCH 02/13] oom: take per file badness into account

["Christian König" <ckoenig.leichtzumerken@gmail.com>]

From: Andrey Grodzovsky <andrey.grodzovsky@amd.com>

Try to make better decisions which process to kill based on
per file OOM badness. For this the per file oom badness is queried from
every file which supports that and divided by the number of references to
that file structure.

Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
---
 mm/oom_kill.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 49d7df39b02d..8a4d05e9568b 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -52,6 +52,8 @@
 #define CREATE_TRACE_POINTS
 #include <trace/events/oom.h>
 
+#include <linux/fdtable.h>
+
 int sysctl_panic_on_oom;
 int sysctl_oom_kill_allocating_task;
 int sysctl_oom_dump_tasks = 1;
@@ -189,6 +191,19 @@ static bool should_dump_unreclaim_slab(void)
 	return (global_node_page_state_pages(NR_SLAB_UNRECLAIMABLE_B) > nr_lru);
 }
 
+/* Sumup how much resources are bound by files opened. */
+static int oom_file_badness(const void *points, struct file *file, unsigned n)
+{
+	long badness;
+
+	if (!file->f_op->oom_badness)
+		return 0;
+
+	badness = file->f_op->oom_badness(file);
+	*((long *)points) += DIV_ROUND_UP(badness, file_count(file));
+	return 0;
+}
+
 /**
  * oom_badness - heuristic function to determine which candidate task to kill
  * @p: task struct of which task we should calculate
@@ -229,6 +244,12 @@ long oom_badness(struct task_struct *p, unsigned long totalpages)
 	 */
 	points = get_mm_rss(p->mm) + get_mm_counter(p->mm, MM_SWAPENTS) +
 		mm_pgtables_bytes(p->mm) / PAGE_SIZE;
+
+	/*
+	 * 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);
 
 	/* Normalize to oom_score_adj units */
-- 
2.25.1