blk-throttle: output some debug info in trace

These info are important to understand what's happening and help debug.

Signed-off-by: Shaohua Li <shli@fb.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 16174f8cb0a177792499f4f25e2b58d57436af90..1f8d62f5e808f44aff353d3f57c66cf3731136a7 100644 (file)
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -1748,12 +1748,18 @@ static bool throtl_tg_is_idle(struct throtl_grp *tg)
         * - IO latency is largely below threshold
         */
        unsigned long time = jiffies_to_usecs(4 * tg->td->throtl_slice);
+       bool ret;
 
        time = min_t(unsigned long, MAX_IDLE_TIME, time);
-       return (ktime_get_ns() >> 10) - tg->last_finish_time > time ||
+       ret = (ktime_get_ns() >> 10) - tg->last_finish_time > time ||
               tg->avg_idletime > tg->idletime_threshold ||
               (tg->latency_target && tg->bio_cnt &&
                tg->bad_bio_cnt * 5 < tg->bio_cnt);
+       throtl_log(&tg->service_queue,
+               "avg_idle=%ld, idle_threshold=%ld, bad_bio=%d, total_bio=%d, is_idle=%d, scale=%d",
+               tg->avg_idletime, tg->idletime_threshold, tg->bad_bio_cnt,
+               tg->bio_cnt, ret, tg->td->scale);
+       return ret;
 }
 
 static bool throtl_tg_can_upgrade(struct throtl_grp *tg)
@@ -1849,6 +1855,7 @@ static void throtl_upgrade_state(struct throtl_data *td)
        struct cgroup_subsys_state *pos_css;
        struct blkcg_gq *blkg;
 
+       throtl_log(&td->service_queue, "upgrade to max");
        td->limit_index = LIMIT_MAX;
        td->low_upgrade_time = jiffies;
        td->scale = 0;
@@ -1871,6 +1878,7 @@ static void throtl_downgrade_state(struct throtl_data *td, int new)
 {
        td->scale /= 2;
 
+       throtl_log(&td->service_queue, "downgrade, scale %d", td->scale);
        if (td->scale) {
                td->low_upgrade_time = jiffies - td->scale * td->throtl_slice;
                return;
@@ -2044,6 +2052,11 @@ static void throtl_update_latency_buckets(struct throtl_data *td)
                td->avg_buckets[i].valid = true;
                last_latency = td->avg_buckets[i].latency;
        }
+
+       for (i = 0; i < LATENCY_BUCKET_SIZE; i++)
+               throtl_log(&td->service_queue,
+                       "Latency bucket %d: latency=%ld, valid=%d", i,
+                       td->avg_buckets[i].latency, td->avg_buckets[i].valid);
 }
 #else
 static inline void throtl_update_latency_buckets(struct throtl_data *td)