Re: [PATCH 1/2] memory: samsung: exynos5422-dmc: Adjust polling interval and uptreshold

[Lukasz Luba]

On 7/10/20 2:49 PM, Bartlomiej Zolnierkiewicz wrote:
> On 7/10/20 2:56 PM, Lukasz Luba wrote:
> > On 7/10/20 1:45 PM, Krzysztof Kozlowski wrote:
> > > On Fri, Jul 10, 2020 at 09:34:45AM +0100, Lukasz Luba wrote:
> > > > Hi Chanwoo,
> > > >
> > > > On 7/9/20 5:08 AM, Chanwoo Choi wrote:
> > > > > Hi Lukasz,
> > > > >
> > > > > On 7/9/20 12:34 AM, Lukasz Luba wrote:
> > > > > > In order to react faster and make better decisions under some workloads,
> > > > > > benchmarking the memory subsystem behavior, adjust the polling interval
> > > > > > and upthreshold value used by the simple_ondemand governor.
> > > > > >
> > > > > > Reported-by: Willy Wolff <willy.mh.wolff.ml@xxxxxxxxx>
> > > > > > Signed-off-by: Lukasz Luba <lukasz.luba@xxxxxxx>
> > > > > > ---
> > > > > >  ÂÂ drivers/memory/samsung/exynos5422-dmc.c | 4 ++--
> > > > > >  ÂÂ 1 file changed, 2 insertions(+), 2 deletions(-)
> > > > > >
> > > > > > diff --git a/drivers/memory/samsung/exynos5422-dmc.c b/drivers/memory/samsung/exynos5422-dmc.c
> > > > > > index 93e9c2429c0d..e03ee35f0ab5 100644
> > > > > > --- a/drivers/memory/samsung/exynos5422-dmc.c
> > > > > > +++ b/drivers/memory/samsung/exynos5422-dmc.c
> > > > > > @@ -1466,10 +1466,10 @@ static int exynos5_dmc_probe(struct platform_device *pdev)
> > > > > >  ÂÂÂÂÂÂÂÂÂÂÂ * Setup default thresholds for the devfreq governor.
> > > > > >  ÂÂÂÂÂÂÂÂÂÂÂ * The values are chosen based on experiments.
> > > > > >  ÂÂÂÂÂÂÂÂÂÂÂ */
> > > > > > -ÂÂÂÂÂÂÂ dmc->gov_data.upthreshold = 30;
> > > > > > +ÂÂÂÂÂÂÂ dmc->gov_data.upthreshold = 10;
> > > > > >  ÂÂÂÂÂÂÂÂÂÂ dmc->gov_data.downdifferential = 5;
> > > > > > -ÂÂÂÂÂÂÂ exynos5_dmc_df_profile.polling_ms = 500;
> > > > > > +ÂÂÂÂÂÂÂ exynos5_dmc_df_profile.polling_ms = 100;
> > > > > >  ÂÂÂÂÂÂ }
> > > > >
> > > > > Reviewed-by: Chanwoo Choi <cw00.choi@xxxxxxxxxxx>
> > > >
> > > > Thank you for the review. Do you think this patch could go through
> > > > your tree together with your patches?
> > > >
> > > > I don't know Krzysztof's opinion about the patch 2/2, but
> > > > I would expect, assuming the patch itself is correct, he would
> > > > like to take it into his next/dt branch.
> > >
> > > In the cover letter you mentioned that this is a follow up for the
> > > Chanwoo's patchset. But are these patches really depending on it? Can
> > > they be picked up independently?
> >
> >
> > They are not heavily dependent on Chanwoo's patches.
> > Yes, they can be picked up independently.
>
> Hmmm, are you sure?

In a sense: in two phases (first the Chanwoo's changes land into
devfreq, then when Krzysztof prepares his topic branches for
arm soc, I assumed Chanwoo's patches are mainline and will be there
already).

> Sure, they will apply fine but without Chanwoo's patches won't they
> cause the dmc driver to use using polling mode with deferred timer
> (unintended/bad behavior) instead of IRQs (current behavior) or
> polling mode with delayed timer (future behavior)?

I was assuming that it will take longer, when Krzysztof is going to pick
patch 2/2, definitely after a while (and it could be also the case for
patch 1/1 if Krzysztof was going to take it).

I think there is no rush and it can go in two phases.

Good point Bartek for clarifying this. I wasn't clear in the messages.
Thank you for keeping eye on this.

Regards,
Lukasz


> Best regards,
> --
> Bartlomiej Zolnierkiewicz
> Samsung R&D Institute Poland
> Samsung Electronics
>
> > I just wanted to mention that the patch 1/2 was produced on the
> > code base which had already applied Chanwoo's patch for DMC.
> > If you like to take both 1/2 and 2/2 into your tree, it's good.
> >
> > Thank you for having a look on this.
> >
> > Regards,
> > Lukasz
> >
> >
> > > The DTS patch must go through arm soc, so I will take it. If it really
> > > depends on driver changes, then it has to wait for next release.
> > >
> > > Best regards,
> > > Krzysztof