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From:   Chengming Zhou <zhouchengming@bytedance.com>
To:     tj@kernel.org, axboe@kernel.dk
Cc:     linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
        Chengming Zhou <zhouchengming@bytedance.com>
Subject: [PATCH 1/2] blk-iocost: remove the second superfluous current_hweight
Date:   Thu,  9 Jun 2022 15:34:49 +0800
Message-Id: <20220609073450.98975-1-zhouchengming@bytedance.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

The commit ac33e91e2dac ("blk-iocost: implement vtime loss compensation")
add the second current_hweight() in the loop of active iocgs list to
get old_hwi to calculate the vtime loss of the iocg.

Since the hwi can't change and the first current_hweight already get
hwa and hwi, so this second superfluous current_hweight() can be
removed. There should be no functional changes.

Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
---
 block/blk-iocost.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 33a11ba971ea..3cda08224d51 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -2238,7 +2238,7 @@ 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;
-		u32 hw_active, hw_inuse;
+		u32 hwa, old_hwi;
 
 		/*
 		 * Collect unused and wind vtime closer to vnow to prevent
@@ -2246,7 +2246,7 @@ static void ioc_timer_fn(struct timer_list *timer)
 		 */
 		vdone = atomic64_read(&iocg->done_vtime);
 		vtime = atomic64_read(&iocg->vtime);
-		current_hweight(iocg, &hw_active, &hw_inuse);
+		current_hweight(iocg, &hwa, &old_hwi);
 
 		/*
 		 * Latency QoS detection doesn't account for IOs which are
@@ -2271,15 +2271,15 @@ static void ioc_timer_fn(struct timer_list *timer)
 
 		/* see whether there's surplus vtime */
 		WARN_ON_ONCE(!list_empty(&iocg->surplus_list));
-		if (hw_inuse < hw_active ||
+		if (old_hwi < hwa ||
 		    (!waitqueue_active(&iocg->waitq) &&
 		     time_before64(vtime, now.vnow - ioc->margins.low))) {
-			u32 hwa, old_hwi, hwm, new_hwi, usage;
+			u32 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),
+					cost_to_abs_cost(vtime - vdone, old_hwi),
 					ioc->vtime_base_rate);
 
 				usage_us = max(usage_us, inflight_us);
@@ -2300,7 +2300,6 @@ static void ioc_timer_fn(struct timer_list *timer)
 			 * Already donating or accumulated enough to start.
 			 * Determine the donation amount.
 			 */
-			current_hweight(iocg, &hwa, &old_hwi);
 			hwm = current_hweight_max(iocg);
 			new_hwi = hweight_after_donation(iocg, old_hwi, hwm,
 							 usage, &now);
-- 
2.36.1