From: Shaohua Li <shli@fb.com>
Date: Tue, 10 May 2016 00:22:15 +0000 (-0700)
Subject: blk-throttle: don't parse cgroup path if trace isn't enabled
X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=59fa0224cfea31dde596e29555de94c961b139f9;p=openwrt%2Fstaging%2Fblogic.git

blk-throttle: don't parse cgroup path if trace isn't enabled

if trace isn't enabled, parsing cgroup path just wastes cpu

Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
---

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 2149a1ddbacf..47a3e540631a 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -211,15 +211,14 @@ static struct throtl_data *sq_to_td(struct throtl_service_queue *sq)
  *
  * The messages are prefixed with "throtl BLKG_NAME" if @sq belongs to a
  * throtl_grp; otherwise, just "throtl".
- *
- * TODO: this should be made a function and name formatting should happen
- * after testing whether blktrace is enabled.
  */
 #define throtl_log(sq, fmt, args...)	do {				\
 	struct throtl_grp *__tg = sq_to_tg((sq));			\
 	struct throtl_data *__td = sq_to_td((sq));			\
 									\
 	(void)__td;							\
+	if (likely(!blk_trace_note_message_enabled(__td->queue)))	\
+		break;							\
 	if ((__tg)) {							\
 		char __pbuf[128];					\
 									\
diff --git a/include/linux/blktrace_api.h b/include/linux/blktrace_api.h
index afc1343df3c7..0f3172b8b225 100644
--- a/include/linux/blktrace_api.h
+++ b/include/linux/blktrace_api.h
@@ -57,6 +57,14 @@ void __trace_note_message(struct blk_trace *, const char *fmt, ...);
 	} while (0)
 #define BLK_TN_MAX_MSG		128
 
+static inline bool blk_trace_note_message_enabled(struct request_queue *q)
+{
+	struct blk_trace *bt = q->blk_trace;
+	if (likely(!bt))
+		return false;
+	return bt->act_mask & BLK_TC_NOTIFY;
+}
+
 extern void blk_add_driver_data(struct request_queue *q, struct request *rq,
 				void *data, size_t len);
 extern int blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
@@ -79,6 +87,7 @@ extern struct attribute_group blk_trace_attr_group;
 # define blk_trace_remove(q)				(-ENOTTY)
 # define blk_add_trace_msg(q, fmt, ...)			do { } while (0)
 # define blk_trace_remove_sysfs(dev)			do { } while (0)
+# define blk_trace_note_message_enabled(q)		(false)
 static inline int blk_trace_init_sysfs(struct device *dev)
 {
 	return 0;