linux-kernel - Re: [PATCH v2 3/4] block, bfq: add support to record request size information

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Message-Id: <6420E679-38C5-4599-AE28-446F927BDB6F@linaro.org>
Date:   Thu, 26 Aug 2021 19:00:51 +0200
From:   Paolo Valente <paolo.valente@...aro.org>
To:     Yu Kuai <yukuai3@...wei.com>
Cc:     axboe@...nel.dk, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, yi.zhang@...wei.com
Subject: Re: [PATCH v2 3/4] block, bfq: add support to record request size
 information



> Il giorno 6 ago 2021, alle ore 04:08, Yu Kuai <yukuai3@...wei.com> ha scritto:
> 
> If bfq keep

keeps

> dispatching requests with same size, the following
> information are

is stored

> stored if CONFIG_BFQ_GROUP_IOSCHED is enabled:
> 
> 1) the size
> 2) the count of requests
> 3) when the first request was dispatched
> 
> These will be used in later patch to support concurrent sync
> io in such situation.
> 
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
> ---
> block/bfq-iosched.c | 15 +++++++++++++++
> block/bfq-iosched.h | 16 ++++++++++++++++
> 2 files changed, 31 insertions(+)
> 
> diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
> index a780205a1be4..7df3fc0ef4ef 100644
> --- a/block/bfq-iosched.c
> +++ b/block/bfq-iosched.c
> @@ -4936,6 +4936,20 @@ static bool bfq_has_work(struct blk_mq_hw_ctx *hctx)
> 		bfq_tot_busy_queues(bfqd) > 0;
> }
> 
> +static void bfq_update_dispatch_size_info(struct bfq_data *bfqd,
> +					  unsigned int size)
> +{
> +#ifdef CONFIG_BFQ_GROUP_IOSCHED
> +	if (bfqd->dispatch_size == size) {
> +		bfqd->dispatch_count++;
> +	} else {
> +		bfqd->dispatch_size = size;
> +		bfqd->dispatch_count = 1;
> +		bfqd->dispatch_time = jiffies;
> +	}
> +#endif
> +}
> +
> static struct request *__bfq_dispatch_request(struct blk_mq_hw_ctx *hctx)
> {
> 	struct bfq_data *bfqd = hctx->queue->elevator->elevator_data;
> @@ -5019,6 +5033,7 @@ static struct request *__bfq_dispatch_request(struct blk_mq_hw_ctx *hctx)
> 		bfqd->rq_in_driver++;
> start_rq:
> 		rq->rq_flags |= RQF_STARTED;
> +		bfq_update_dispatch_size_info(bfqd, blk_rq_bytes(rq));
> 	}
> exit:
> 	return rq;
> diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h
> index 610769214f72..9ab498839e7c 100644
> --- a/block/bfq-iosched.h
> +++ b/block/bfq-iosched.h
> @@ -777,6 +777,22 @@ struct bfq_data {
> 	 * function)
> 	 */
> 	unsigned int word_depths[2][2];
> +
> +#ifdef CONFIG_BFQ_GROUP_IOSCHED
> +	/* the size of last dispatched request */
> +	unsigned int dispatch_size;
> +	/*
> +	 * If bfq keep dispatching requests with same size, this store the

keeps ... stores

> +	 * count of requests. We use unsigned long here, so we don't care
> +	 * about overflow.
> +	 */
> +	unsigned long dispatch_count;
> +	/*
> +	 * If bfq keep dispatching requests with same size, this store the

keeps ... stores

Thanks,
Paolo

> +	 * time when the first request was dispatched.
> +	 */
> +	unsigned long dispatch_time;
> +#endif
> };
> 
> enum bfqq_state_flags {
> -- 
> 2.31.1
>