linux-kernel - [PATCH 5/7] blk-iocost: Move the usage ratio calculation to the correct place

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Message-Id: <89a6e1223944e96e0e5e001191d87dd8079345c8.1606186717.git.baolin.wang@linux.alibaba.com>
Date:   Tue, 24 Nov 2020 11:33:34 +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 5/7] 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 | 37 +++++++++++++++++++------------------
 1 file changed, 19 insertions(+), 18 deletions(-)

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 5305afd..e36cd8e 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -2200,24 +2200,6 @@ 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 ||
@@ -2225,6 +2207,25 @@ static void ioc_timer_fn(struct timer_list *timer)
 		     time_before64(vtime, now.vnow - ioc->margins.low))) {
 			u32 hwa, old_hwi, hwm, new_hwi;
 
+			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.
 			 * Determine the donation amount.
-- 
1.8.3.1