linux-kernel - [PATCH v2 3/5] blk-iocost: Move the usage ratio calculation to the correct place

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Date:   Thu, 26 Nov 2020 16:16:13 +0800
From:   Baolin Wang <baolin.wang@...ux.alibaba.com>
To:     axboe@...nel.dk, tj@...nel.org
Cc:     baolin.wang@...ux.alibaba.com, baolin.wang7@...il.com,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 3/5] blk-iocost: Move the usage ratio calculation to the correct place

We only use the hweight based usage ratio to calculate the new
hweight_inuse of the iocg to decide if this iocg can donate some
surplus vtime.

Thus move the usage ratio calculation to the correct place to
avoid unnecessary calculation for some vtime shortage iocgs.

Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
---
 block/blk-iocost.c | 44 +++++++++++++++++++++++---------------------
 1 file changed, 23 insertions(+), 21 deletions(-)

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 103ccbd..a926179 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -2168,8 +2168,8 @@ static void ioc_timer_fn(struct timer_list *timer)
 
 	/* calc usage and see whether some weights need to be moved around */
 	list_for_each_entry(iocg, &ioc->active_iocgs, active_list) {
-		u64 vdone, vtime, usage_us, usage_dur;
-		u32 usage, hw_active, hw_inuse;
+		u64 vdone, vtime, usage_us;
+		u32 hw_active, hw_inuse;
 
 		/*
 		 * Collect unused and wind vtime closer to vnow to prevent
@@ -2200,30 +2200,32 @@ static void ioc_timer_fn(struct timer_list *timer)
 		usage_us = iocg->usage_delta_us;
 		usage_us_sum += usage_us;
 
-		if (vdone != vtime) {
-			u64 inflight_us = DIV64_U64_ROUND_UP(
-				cost_to_abs_cost(vtime - vdone, hw_inuse),
-				ioc->vtime_base_rate);
-			usage_us = max(usage_us, inflight_us);
-		}
-
-		/* convert to hweight based usage ratio */
-		if (time_after64(iocg->activated_at, ioc->period_at))
-			usage_dur = max_t(u64, now.now - iocg->activated_at, 1);
-		else
-			usage_dur = max_t(u64, now.now - ioc->period_at, 1);
-
-		usage = clamp_t(u32,
-				DIV64_U64_ROUND_UP(usage_us * WEIGHT_ONE,
-						   usage_dur),
-				1, WEIGHT_ONE);
-
 		/* see whether there's surplus vtime */
 		WARN_ON_ONCE(!list_empty(&iocg->surplus_list));
 		if (hw_inuse < hw_active ||
 		    (!waitqueue_active(&iocg->waitq) &&
 		     time_before64(vtime, now.vnow - ioc->margins.low))) {
-			u32 hwa, old_hwi, hwm, new_hwi;
+			u32 hwa, old_hwi, hwm, new_hwi, usage;
+			u64 usage_dur;
+
+			if (vdone != vtime) {
+				u64 inflight_us = DIV64_U64_ROUND_UP(
+					cost_to_abs_cost(vtime - vdone, hw_inuse),
+					ioc->vtime_base_rate);
+
+				usage_us = max(usage_us, inflight_us);
+			}
+
+			/* convert to hweight based usage ratio */
+			if (time_after64(iocg->activated_at, ioc->period_at))
+				usage_dur = max_t(u64, now.now - iocg->activated_at, 1);
+			else
+				usage_dur = max_t(u64, now.now - ioc->period_at, 1);
+
+			usage = clamp_t(u32,
+				DIV64_U64_ROUND_UP(usage_us * WEIGHT_ONE,
+						   usage_dur),
+				1, WEIGHT_ONE);
 
 			/*
 			 * Already donating or accumulated enough to start.
-- 
1.8.3.1