linux-kernel - Re: [PATCH V2 2/2] mmc: hsq: dynamic adjustment of hsq->depth

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Message-ID: <CAPDyKFriZ_uu-WACjqXK5um1bYJSDaHsghOMGwwPJXM8pYCoGw@mail.gmail.com>
Date:   Thu, 24 Aug 2023 12:36:32 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Wenchao Chen <wenchao.chen@...soc.com>
Cc:     linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        wenchao.chen666@...il.com, zhenxiong.lai@...soc.com,
        yuelin.tang@...soc.com
Subject: Re: [PATCH V2 2/2] mmc: hsq: dynamic adjustment of hsq->depth

On Wed, 23 Aug 2023 at 08:18, Wenchao Chen <wenchao.chen@...soc.com> wrote:
>
> Increasing hsq_depth improves random write performance.
>
> Signed-off-by: Wenchao Chen <wenchao.chen@...soc.com>
> ---
>  drivers/mmc/host/mmc_hsq.c | 26 ++++++++++++++++++++++++++
>  drivers/mmc/host/mmc_hsq.h |  2 ++
>  2 files changed, 28 insertions(+)
>
> diff --git a/drivers/mmc/host/mmc_hsq.c b/drivers/mmc/host/mmc_hsq.c
> index 8556cacb21a1..8682a3d16a76 100644
> --- a/drivers/mmc/host/mmc_hsq.c
> +++ b/drivers/mmc/host/mmc_hsq.c
> @@ -21,6 +21,30 @@ static void mmc_hsq_retry_handler(struct work_struct *work)
>         mmc->ops->request(mmc, hsq->mrq);
>  }
>
> +static void mmc_hsq_modify_threshold(struct mmc_hsq *hsq)
> +{
> +       struct mmc_host *mmc = hsq->mmc;
> +       struct mmc_request *mrq;
> +       struct hsq_slot *slot;
> +       int need_change = 0;
> +       int tag;
> +
> +       for (tag = 0; tag < HSQ_NUM_SLOTS; tag++) {
> +               slot = &hsq->slot[tag];
> +               mrq = slot->mrq;
> +               if (mrq && mrq->data && (mrq->data->blocks == HSQ_DATA_IS_4K)

This assumes mrq->data->blksz is 512 (which at least for now is always
the case), but perhaps better to compute the request size instead?
Hence:

"mrq->data->blksz * mrq->data->blocks == 4096"

> +                               && (mrq->data->flags & MMC_DATA_WRITE))
> +                       need_change++;
> +               else
> +                       break;
> +       }
> +
> +       if (need_change > 1)
> +               mmc->hsq_depth = HSQ_PERFORMANCE_DEPTH;
> +       else
> +               mmc->hsq_depth = HSQ_NORMAL_DEPTH;
> +}
> +
>  static void mmc_hsq_pump_requests(struct mmc_hsq *hsq)
>  {
>         struct mmc_host *mmc = hsq->mmc;
> @@ -42,6 +66,8 @@ static void mmc_hsq_pump_requests(struct mmc_hsq *hsq)
>                 return;
>         }
>
> +       mmc_hsq_modify_threshold(hsq);
> +
>         slot = &hsq->slot[hsq->next_tag];
>         hsq->mrq = slot->mrq;
>         hsq->qcnt--;
> diff --git a/drivers/mmc/host/mmc_hsq.h b/drivers/mmc/host/mmc_hsq.h
> index aa5c4543b55f..fc031e38f1e0 100644
> --- a/drivers/mmc/host/mmc_hsq.h
> +++ b/drivers/mmc/host/mmc_hsq.h
> @@ -10,6 +10,8 @@
>   * flight to avoid a long latency.
>   */
>  #define HSQ_NORMAL_DEPTH       2
> +#define HSQ_PERFORMANCE_DEPTH  5
> +#define HSQ_DATA_IS_4K 8

Perhaps re-phrase the comment a few lines above to explain why/when
'5' can be good too.

>
>  struct hsq_slot {
>         struct mmc_request *mrq;

Kind regards
Uffe