blk-iocost: combine local_stat and desc_stat to stat

When we flush usage, wait, indebt stat in iocg_flush_stat(), we use
local_stat and desc_stat, which has no point since the leaf iocg
only has local_stat and the inner iocg only has desc_stat. Also
we don't need to flush percpu abs_vusage for these inner iocgs.

This patch combine local_stat and desc_stat to stat, only flush
percpu abs_vusage for active leaf iocgs, then build inner walk
list to propagate.

Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20220510034757.21761-1-zhouchengming@bytedance.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-iocost.c

@@ -533,8 +533,7 @@ struct ioc_gq {
 
 	/* statistics */
 	struct iocg_pcpu_stat __percpu	*pcpu_stat;
-	struct iocg_stat		local_stat;
+	struct iocg_stat		stat;
-	struct iocg_stat		desc_stat;
 	struct iocg_stat		last_stat;
 	u64				last_stat_abs_vusage;
 	u64				usage_delta_us;
@@ -1371,7 +1370,7 @@ static bool iocg_kick_delay(struct ioc_gq *iocg, struct ioc_now *now)
 		return true;
 	} else {
 		if (iocg->indelay_since) {
-			iocg->local_stat.indelay_us += now->now - iocg->indelay_since;
+			iocg->stat.indelay_us += now->now - iocg->indelay_since;
 			iocg->indelay_since = 0;
 		}
 		iocg->delay = 0;
@@ -1419,7 +1418,7 @@ static void iocg_pay_debt(struct ioc_gq *iocg, u64 abs_vpay,
 
 	/* if debt is paid in full, restore inuse */
 	if (!iocg->abs_vdebt) {
-		iocg->local_stat.indebt_us += now->now - iocg->indebt_since;
+		iocg->stat.indebt_us += now->now - iocg->indebt_since;
 		iocg->indebt_since = 0;
 
 		propagate_weights(iocg, iocg->active, iocg->last_inuse,
@@ -1513,7 +1512,7 @@ static void iocg_kick_waitq(struct ioc_gq *iocg, bool pay_debt,
 
 	if (!waitqueue_active(&iocg->waitq)) {
 		if (iocg->wait_since) {
-			iocg->local_stat.wait_us += now->now - iocg->wait_since;
+			iocg->stat.wait_us += now->now - iocg->wait_since;
 			iocg->wait_since = 0;
 		}
 		return;
@@ -1641,11 +1640,30 @@ static void iocg_build_inner_walk(struct ioc_gq *iocg,
 	}
 }
 
+/* propagate the deltas to the parent */
+static void iocg_flush_stat_upward(struct ioc_gq *iocg)
+{
+	if (iocg->level > 0) {
+		struct iocg_stat *parent_stat =
+			&iocg->ancestors[iocg->level - 1]->stat;
+
+		parent_stat->usage_us +=
+			iocg->stat.usage_us - iocg->last_stat.usage_us;
+		parent_stat->wait_us +=
+			iocg->stat.wait_us - iocg->last_stat.wait_us;
+		parent_stat->indebt_us +=
+			iocg->stat.indebt_us - iocg->last_stat.indebt_us;
+		parent_stat->indelay_us +=
+			iocg->stat.indelay_us - iocg->last_stat.indelay_us;
+	}
+
+	iocg->last_stat = iocg->stat;
+}
+
 /* collect per-cpu counters and propagate the deltas to the parent */
-static void iocg_flush_stat_one(struct ioc_gq *iocg, struct ioc_now *now)
+static void iocg_flush_stat_leaf(struct ioc_gq *iocg, struct ioc_now *now)
 {
 	struct ioc *ioc = iocg->ioc;
-	struct iocg_stat new_stat;
 	u64 abs_vusage = 0;
 	u64 vusage_delta;
 	int cpu;
@@ -1661,34 +1679,9 @@ static void iocg_flush_stat_one(struct ioc_gq *iocg, struct ioc_now *now)
 	iocg->last_stat_abs_vusage = abs_vusage;
 
 	iocg->usage_delta_us = div64_u64(vusage_delta, ioc->vtime_base_rate);
-	iocg->local_stat.usage_us += iocg->usage_delta_us;
+	iocg->stat.usage_us += iocg->usage_delta_us;
 
-	/* propagate upwards */
+	iocg_flush_stat_upward(iocg);
-	new_stat.usage_us =
-		iocg->local_stat.usage_us + iocg->desc_stat.usage_us;
-	new_stat.wait_us =
-		iocg->local_stat.wait_us + iocg->desc_stat.wait_us;
-	new_stat.indebt_us =
-		iocg->local_stat.indebt_us + iocg->desc_stat.indebt_us;
-	new_stat.indelay_us =
-		iocg->local_stat.indelay_us + iocg->desc_stat.indelay_us;
-
-	/* propagate the deltas to the parent */
-	if (iocg->level > 0) {
-		struct iocg_stat *parent_stat =
-			&iocg->ancestors[iocg->level - 1]->desc_stat;
-
-		parent_stat->usage_us +=
-			new_stat.usage_us - iocg->last_stat.usage_us;
-		parent_stat->wait_us +=
-			new_stat.wait_us - iocg->last_stat.wait_us;
-		parent_stat->indebt_us +=
-			new_stat.indebt_us - iocg->last_stat.indebt_us;
-		parent_stat->indelay_us +=
-			new_stat.indelay_us - iocg->last_stat.indelay_us;
-	}
-
-	iocg->last_stat = new_stat;
 }
 
 /* get stat counters ready for reading on all active iocgs */
@@ -1699,13 +1692,13 @@ static void iocg_flush_stat(struct list_head *target_iocgs, struct ioc_now *now)
 
 	/* flush leaves and build inner node walk list */
 	list_for_each_entry(iocg, target_iocgs, active_list) {
-		iocg_flush_stat_one(iocg, now);
+		iocg_flush_stat_leaf(iocg, now);
 		iocg_build_inner_walk(iocg, &inner_walk);
 	}
 
 	/* keep flushing upwards by walking the inner list backwards */
 	list_for_each_entry_safe_reverse(iocg, tiocg, &inner_walk, walk_list) {
-		iocg_flush_stat_one(iocg, now);
+		iocg_flush_stat_upward(iocg);
 		list_del_init(&iocg->walk_list);
 	}
 }
@@ -2152,16 +2145,16 @@ static int ioc_check_iocgs(struct ioc *ioc, struct ioc_now *now)
 
 		/* flush wait and indebt stat deltas */
 		if (iocg->wait_since) {
-			iocg->local_stat.wait_us += now->now - iocg->wait_since;
+			iocg->stat.wait_us += now->now - iocg->wait_since;
 			iocg->wait_since = now->now;
 		}
 		if (iocg->indebt_since) {
-			iocg->local_stat.indebt_us +=
+			iocg->stat.indebt_us +=
 				now->now - iocg->indebt_since;
 			iocg->indebt_since = now->now;
 		}
 		if (iocg->indelay_since) {
-			iocg->local_stat.indelay_us +=
+			iocg->stat.indelay_us +=
 				now->now - iocg->indelay_since;
 			iocg->indelay_since = now->now;
 		}