ANDROID: vendor_hooks: add hook and OEM data for slab shrink

Some shrinker add lock in count_objects() may cause lock contention
issues and lead all task stall on slab shrink. Add vendor hook in
do_shrink_slab() for shrinker->count_objects() latency measuring.

Add 3 oem data in shrink_control struct. Two is for
shrinker->count_objects() and shrinker->scan_objects() latency
measuring, other one to store priority, some shrinker know the reclaimer
priority can control the memory reclaim more better.

Bug: 188684131

Change-Id: I80e9d90179bb52a99c54d9a067c6fcee835bb2ad
Signed-off-by: rongqianfeng <rongqianfeng@vivo.com>
diff --git a/mm/vmscan.c b/mm/vmscan.c
index de68f287..d37724d 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -716,6 +716,8 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
 					  : SHRINK_BATCH;
 	long scanned = 0, next_deferred;
 
+	trace_android_vh_do_shrink_slab(shrinker, shrinkctl, priority);
+
 	freeable = shrinker->count_objects(shrinker, shrinkctl);
 	if (freeable == 0 || freeable == SHRINK_EMPTY)
 		return freeable;