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

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Message-ID: <6375ee42-a9c3-4cb9-b14e-856565dd8525@kernel.org>
Date: Sat, 26 Jul 2025 02:07:33 +0800
From: Yu Kuai <yukuai@...nel.org>
To: Tang Yizhou <yizhou.tang@...pee.com>, axboe@...nel.dk, hch@....de,
 jack@...e.cz
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
 tangyeechou@...il.com
Subject: Re: [PATCH 1/3] blk-wbt: Optimize wbt_done() for non-throttled writes

Hi,

在 2025/7/24 16:29, Tang Yizhou 写道:
> 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));
At lease this is correct logically.

Reviewed-by: Yu Kuai <yukuai3@...wei.com>