blk-iocost: Trace vtime_base_rate instead of vtime_rate

Since commit ac33e91 ("blk-iocost: implement vtime loss
compensation") rename original vtime_rate to vtime_base_rate
and current vtime_rate is original vtime_rate with compensation.
The current rate showed in tracepoint is mixed with vtime_rate
and vtime_base_rate:
1) In function ioc_adjust_base_vrate, the first trace_iocost_ioc_vrate_adj
shows vtime_rate, the second trace_iocost_ioc_vrate_adj shows
vtime_base_rate.
2) In function iocg_activate shows vtime_rate by calling
TRACE_IOCG_PATH(iocg_activate...
3) In function ioc_check_iocgs shows vtime_rate by calling
TRACE_IOCG_PATH(iocg_idle...

Trace vtime_base_rate instead of vtime_rate as:
1) Before commit ac33e91 ("blk-iocost: implement vtime loss
compensation"), the traced rate is without compensation, so still
show rate without compensation.
2) The vtime_base_rate is more stable while vtime_rate heavily depends on
excess budeget on current period which may change abruptly in next period.

Signed-off-by: Kemeng Shi <shikemeng@huawei.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20221018121932.10792-4-shikemeng@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-iocost.c

@@ -977,7 +977,7 @@ static void ioc_adjust_base_vrate(struct ioc *ioc, u32 rq_wait_pct,
 
 	if (!ioc->busy_level || (ioc->busy_level < 0 && nr_lagging)) {
 		if (ioc->busy_level != prev_busy_level || nr_lagging)
-			trace_iocost_ioc_vrate_adj(ioc, atomic64_read(&ioc->vtime_rate),
+			trace_iocost_ioc_vrate_adj(ioc, vrate,
 						   missed_ppm, rq_wait_pct,
 						   nr_lagging, nr_shortages);
 

include/trace/events/iocost.h

@@ -38,7 +38,7 @@ DECLARE_EVENT_CLASS(iocost_iocg_state,
 		__assign_str(cgroup, path);
 		__entry->now = now->now;
 		__entry->vnow = now->vnow;
-		__entry->vrate = now->vrate;
+		__entry->vrate = iocg->ioc->vtime_base_rate;
 		__entry->last_period = last_period;
 		__entry->cur_period = cur_period;
 		__entry->vtime = vtime;
@@ -160,7 +160,7 @@ TRACE_EVENT(iocost_ioc_vrate_adj,
 
 	TP_fast_assign(
 		__assign_str(devname, ioc_name(ioc));
-		__entry->old_vrate = atomic64_read(&ioc->vtime_rate);
+		__entry->old_vrate = ioc->vtime_base_rate;
 		__entry->new_vrate = new_vrate;
 		__entry->busy_level = ioc->busy_level;
 		__entry->read_missed_ppm = missed_ppm[READ];