linux-kernel - [PATCH 1/3] blk-wbt: Optimize wbt

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Message-Id: <20250724083001.362882-2-yizhou.tang@shopee.com>
Date: Thu, 24 Jul 2025 16:29:59 +0800
From: Tang Yizhou <yizhou.tang@...pee.com>
To: axboe@...nel.dk,
	hch@....de,
	jack@...e.cz
Cc: linux-block@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	tangyeechou@...il.com,
	Tang Yizhou <yizhou.tang@...pee.com>
Subject: [PATCH 1/3] blk-wbt: Optimize wbt_done() for non-throttled writes

From: Tang Yizhou <yizhou.tang@...pee.com>

In the current implementation, the sync_cookie and last_cookie members of
struct rq_wb are used only by read requests and not by non-throttled write
requests. Based on this, we can optimize wbt_done() by removing one if
condition check for non-throttled write requests.

Signed-off-by: Tang Yizhou <yizhou.tang@...pee.com>
---
 block/blk-wbt.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/block/blk-wbt.c b/block/blk-wbt.c
index a50d4cd55f41..30886d44f6cd 100644
--- a/block/blk-wbt.c
+++ b/block/blk-wbt.c
@@ -248,13 +248,14 @@ static void wbt_done(struct rq_qos *rqos, struct request *rq)
 	struct rq_wb *rwb = RQWB(rqos);
 
 	if (!wbt_is_tracked(rq)) {
-		if (rwb->sync_cookie == rq) {
-			rwb->sync_issue = 0;
-			rwb->sync_cookie = NULL;
-		}
+		if (wbt_is_read(rq)) {
+			if (rwb->sync_cookie == rq) {
+				rwb->sync_issue = 0;
+				rwb->sync_cookie = NULL;
+			}
 
-		if (wbt_is_read(rq))
 			wb_timestamp(rwb, &rwb->last_comp);
+		}
 	} else {
 		WARN_ON_ONCE(rq == rwb->sync_cookie);
 		__wbt_done(rqos, wbt_flags(rq));
-- 
2.25.1