linux-kernel - Re: [PATCH V3 2/2] mmc: hsq: dynamic adjustment of hsq->depth

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Date:   Fri, 15 Sep 2023 19:38:04 +0800
From:   Wenchao Chen <wenchao.chen666@...il.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Wenchao Chen <wenchao.chen@...soc.com>, linux-mmc@...r.kernel.org,
        linux-kernel@...r.kernel.org, zhenxiong.lai@...soc.com,
        yuelin.tang@...soc.com
Subject: Re: [PATCH V3 2/2] mmc: hsq: dynamic adjustment of hsq->depth

On Thu, 14 Sept 2023 at 20:57, Ulf Hansson <ulf.hansson@...aro.org> wrote:
>
> On Tue, 29 Aug 2023 at 04:05, 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 | 27 +++++++++++++++++++++++++++
> >  drivers/mmc/host/mmc_hsq.h |  5 +++++
> >  2 files changed, 32 insertions(+)
> >
> > diff --git a/drivers/mmc/host/mmc_hsq.c b/drivers/mmc/host/mmc_hsq.c
> > index 8556cacb21a1..0984c39108ba 100644
> > --- a/drivers/mmc/host/mmc_hsq.c
> > +++ b/drivers/mmc/host/mmc_hsq.c
> > @@ -21,6 +21,31 @@ 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;
>
> Rather than using a variable to keep track of this, why not just do
> the below here?
>
> mmc->hsq_depth = HSQ_NORMAL_DEPTH;
>
> > +       int tag;
> > +
> > +       for (tag = 0; tag < HSQ_NUM_SLOTS; tag++) {
> > +               slot = &hsq->slot[tag];
> > +               mrq = slot->mrq;
> > +               if (mrq && mrq->data &&
> > +                       (mrq->data->blksz * mrq->data->blocks == 4096) &&
> > +                       (mrq->data->flags & MMC_DATA_WRITE))
> > +                       need_change++;
>
> And following above, then we can do the below here:
> mmc->hsq_depth = HSQ_PERFORMANCE_DEPTH;
> break;
>
> That should simplify and make this more efficient too, right?
>

Yes, you are right. But need_change = 2, it means more reqs are allowed.
Alternatively, modify it like this:
mmc->hsq_depth = (need_change > 1)  ? HSQ_PERFORMANCE_DEPTH : HSQ_NORMAL_DEPTH;

> > +               else
> > +                       break;
> > +       }
> > +
> > +       if (need_change > 1)
> > +               mmc->hsq_depth = HSQ_PERFORMANCE_DEPTH;
> > +       else
> > +               mmc->hsq_depth = HSQ_NORMAL_DEPTH;
> > +}
> > +
>
> [...]
>
> Kind regards
> Uffe