debugobjects: Export max loops counter

__debug_check_no_obj_freed() can be an expensive operation depending on the
size of memory freed. It already exports the maximum chain walk length via
debugfs, but this only records the maximum of a single memory chunk.

Though there is no information about the total number of objects inspected
for a __debug_check_no_obj_freed() operation, which might be significantly
larger when a huge memory region is freed.

Aggregate the number of objects inspected for a single invocation of
__debug_check_no_obj_freed() and export it via sysfs.

The resulting output of /sys/kernel/debug/debug_objects/stats looks like:

max_chain     :121
max_checked   :543267
warnings      :0
fixups        :0
pool_free     :1764
pool_min_free :341
pool_used     :86438
pool_max_used :268887
objs_allocated:6068254
objs_freed    :5981076

[ tglx: Renamed the variable to max_checked and adjusted changelog ]

Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: longman@redhat.com
Link: https://lkml.kernel.org/r/1517872708-24207-2-git-send-email-yang.shi@linux.alibaba.com

1 files changed, 8 insertions, 1 deletions

diff --git a/lib/debugobjects.c b/lib/debugobjects.c
index 2f5349c6e81a..f6d57a11c927 100644
--- a/lib/debugobjects.c
+++ b/lib/debugobjects.c
@@ -50,6 +50,7 @@ static int			obj_pool_max_used;
 static struct kmem_cache        *obj_cache;
 
 static int                      debug_objects_maxchain __read_mostly;
+static int                      debug_objects_maxchecked __read_mostly;
 static int                      debug_objects_fixups __read_mostly;
 static int                      debug_objects_warnings __read_mostly;
 static int                      debug_objects_enabled __read_mostly
@@ -720,7 +721,7 @@ static void __debug_check_no_obj_freed(const void *address, unsigned long size)
         enum debug_obj_state state;
         struct debug_bucket *db;
         struct debug_obj *obj;
-        int cnt;
+        int cnt, objs_checked = 0;
 
         saddr = (unsigned long) address;
         eaddr = saddr + size;
@@ -765,7 +766,12 @@ repeat:
 
                 if (cnt > debug_objects_maxchain)
                         debug_objects_maxchain = cnt;
+
+                objs_checked += cnt;
         }
+
+        if (objs_checked > debug_objects_maxchecked)
+                debug_objects_maxchecked = objs_checked;
 }
 
 void debug_check_no_obj_freed(const void *address, unsigned long size)
@@ -780,6 +786,7 @@ void debug_check_no_obj_freed(const void *address, unsigned long size)
 static int debug_stats_show(struct seq_file *m, void *v)
 {
         seq_printf(m, "max_chain     :%d\n", debug_objects_maxchain);
+        seq_printf(m, "max_checked   :%d\n", debug_objects_maxchecked);
         seq_printf(m, "warnings      :%d\n", debug_objects_warnings);
         seq_printf(m, "fixups        :%d\n", debug_objects_fixups);
         seq_printf(m, "pool_free     :%d\n", obj_pool_free);