linux-kernel - [PATCH 4/7] blk-iocost: Add a flag to indicate if need update hwi

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Date:   Tue, 24 Nov 2020 11:33:33 +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 4/7] blk-iocost: Add a flag to indicate if need update hwi

We can get the hwa and hwi at one time if no debt need to pay off,
thus add a flag to indicate if the hw_inuse has been changed and
need to update, which can avoid calling current_hweight() twice
for no debt iocgs.

Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
---
 block/blk-iocost.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 089f3fe..5305afd 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -1405,10 +1405,11 @@ static void iocg_kick_waitq(struct ioc_gq *iocg, bool pay_debt,
 	u64 vshortage, expires, oexpires;
 	s64 vbudget;
 	u32 hwa;
+	bool need_update_hwi = false;
 
 	lockdep_assert_held(&iocg->waitq.lock);
 
-	current_hweight(iocg, &hwa, NULL);
+	current_hweight(iocg, &hwa, &ctx.hw_inuse);
 	vbudget = now->vnow - atomic64_read(&iocg->vtime);
 
 	/* pay off debt */
@@ -1423,6 +1424,7 @@ static void iocg_kick_waitq(struct ioc_gq *iocg, bool pay_debt,
 		atomic64_add(vpay, &iocg->done_vtime);
 		iocg_pay_debt(iocg, abs_vpay, now);
 		vbudget -= vpay;
+		need_update_hwi = true;
 	}
 
 	if (iocg->abs_vdebt || iocg->delay)
@@ -1445,7 +1447,8 @@ static void iocg_kick_waitq(struct ioc_gq *iocg, bool pay_debt,
 	 * after the above debt payment.
 	 */
 	ctx.vbudget = vbudget;
-	current_hweight(iocg, NULL, &ctx.hw_inuse);
+	if (need_update_hwi)
+		current_hweight(iocg, NULL, &ctx.hw_inuse);
 
 	__wake_up_locked_key(&iocg->waitq, TASK_NORMAL, &ctx);
 
-- 
1.8.3.1