linux-kernel - [PATCH v2 5/6] mm/slub: sort debugfs output by frequency of stack traces

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Date:   Wed,  2 Mar 2022 18:31:21 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     David Rientjes <rientjes@...gle.com>,
        Christoph Lameter <cl@...ux.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Pekka Enberg <penberg@...nel.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        patches@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Oliver Glitta <glittao@...il.com>,
        Faiyaz Mohammed <faiyazm@...eaurora.org>,
        Marco Elver <elver@...gle.com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>,
        Imran Khan <imran.f.khan@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH v2 5/6] mm/slub: sort debugfs output by frequency of stack traces

From: Oliver Glitta <glittao@...il.com>

Sort the output of debugfs alloc_traces and free_traces by the frequency
of allocation/freeing stack traces. Most frequently used stack traces
will be printed first, e.g. for easier memory leak debugging.

Signed-off-by: Oliver Glitta <glittao@...il.com>
Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
Reviewed-and-tested-by: Hyeonggon Yoo <42.hyeyoo@...il.com>
---
 mm/slub.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/mm/slub.c b/mm/slub.c
index 25138cd7a4ef..39da762fbceb 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -38,6 +38,7 @@
 #include <linux/memcontrol.h>
 #include <linux/random.h>
 #include <kunit/test.h>
+#include <linux/sort.h>
 
 #include <linux/debugfs.h>
 #include <trace/events/kmem.h>
@@ -6149,6 +6150,17 @@ static void *slab_debugfs_next(struct seq_file *seq, void *v, loff_t *ppos)
 	return NULL;
 }
 
+static int cmp_loc_by_count(const void *a, const void *b, const void *data)
+{
+	struct location *loc1 = (struct location *)a;
+	struct location *loc2 = (struct location *)b;
+
+	if (loc1->count > loc2->count)
+		return -1;
+	else
+		return 1;
+}
+
 static void *slab_debugfs_start(struct seq_file *seq, loff_t *ppos)
 {
 	struct loc_track *t = seq->private;
@@ -6210,6 +6222,10 @@ static int slab_debug_trace_open(struct inode *inode, struct file *filep)
 		spin_unlock_irqrestore(&n->list_lock, flags);
 	}
 
+	/* Sort locations by count */
+	sort_r(t->loc, t->count, sizeof(struct location),
+		cmp_loc_by_count, NULL, NULL);
+
 	bitmap_free(obj_map);
 	return 0;
 }
-- 
2.35.1