iocost: better trace vrate changes

vrate_adj tracepoint traces vrate changes; however, it does so only
when busy_level is non-zero.  busy_level turning to zero can sometimes
be as interesting an event.  This patch also enables vrate_adj
tracepoint on other vrate related events - busy_level changes and
non-zero nr_lagging.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 3b39deb8b9f820620b86c0d964b30eb1dbb362b6..32d4d6d86a99404633ebf27b8ddcf2030afedab8 100644 (file)
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -1343,7 +1343,7 @@ static void ioc_timer_fn(struct timer_list *timer)
        u32 ppm_wthr = MILLION - ioc->params.qos[QOS_WPPM];
        u32 missed_ppm[2], rq_wait_pct;
        u64 period_vtime;
-       int i;
+       int prev_busy_level, i;
 
        /* how were the latencies during the period? */
        ioc_lat_stat(ioc, missed_ppm, &rq_wait_pct);
@@ -1531,6 +1531,7 @@ skip_surplus_transfers:
         * and experiencing shortages but not surpluses, we're too stingy
         * and should increase vtime rate.
         */
+       prev_busy_level = ioc->busy_level;
        if (rq_wait_pct > RQ_WAIT_BUSY_PCT ||
            missed_ppm[READ] > ppm_rthr ||
            missed_ppm[WRITE] > ppm_wthr) {
@@ -1592,6 +1593,10 @@ skip_surplus_transfers:
                atomic64_set(&ioc->vtime_rate, vrate);
                ioc->inuse_margin_vtime = DIV64_U64_ROUND_UP(
                        ioc->period_us * vrate * INUSE_MARGIN_PCT, 100);
+       } else if (ioc->busy_level != prev_busy_level || nr_lagging) {
+               trace_iocost_ioc_vrate_adj(ioc, atomic64_read(&ioc->vtime_rate),
+                                          &missed_ppm, rq_wait_pct, nr_lagging,
+                                          nr_shortages, nr_surpluses);
        }
 
        ioc_refresh_params(ioc, false);