linux-kernel - Re: [PATCH v2 0/9] Add Host control mode to HPB

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Message-ID: <ec32248a3e56eef83744cd4844210d347add27d3.camel@gmail.com>
Date:   Fri, 05 Feb 2021 12:36:24 +0100
From:   Bean Huo <huobean@...il.com>
To:     Avri Altman <avri.altman@....com>,
        "James E . J . Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     gregkh@...uxfoundation.org, Bart Van Assche <bvanassche@....org>,
        yongmyung lee <ymhungry.lee@...sung.com>,
        Daejun Park <daejun7.park@...sung.com>,
        alim.akhtar@...sung.com, asutoshd@...eaurora.org,
        Zang Leigang <zangleigang@...ilicon.com>,
        Avi Shchislowski <avi.shchislowski@....com>,
        Bean Huo <beanhuo@...ron.com>, cang@...eaurora.org,
        stanley.chu@...iatek.com
Subject: Re: [PATCH v2 0/9] Add Host control mode to HPB

On Tue, 2021-02-02 at 10:29 +0200, Avri Altman wrote:
> v1 -> v2:
>  - attend Greg's and Daejun's comments
>  - add patch 9 making host mode parameters configurable
>  - rebase on Daejun's v19
> 
> 
> The HPB spec defines 2 control modes - device control mode and host
> control mode. In oppose to device control mode, in which the host
> obey
> to whatever recommendation received from the device - In host control
> mode, the host uses its own algorithms to decide which regions should
> be activated or inactivated.
> 
> We kept the host managed heuristic simple and concise.
> 
> Aside from adding a by-spec functionality, host control mode entails
> some further potential benefits: makes the hpb logic transparent and
> readable, while allow tuning / scaling its various parameters, and
> utilize system-wide info to optimize HPB potential.

Hi Avri
In addition to the above advantage of HPB device mode, would you please
share the performance comparison data with host mode? that will draw
more attention, since you mentioned "you tested on Galaxy S20, and
Xiaomi Mi10 pro", I think you have this kind of data.

Your HPB host driver sits in the ufs driver. Since my HPB host mode
driver is also implemented in the UFS driver layer, I did test my HPB
driver between device mode and host mode. Saw there is an improvement,
but not significant. If you can share your HPB drviver data, that will
be awesome.

Kind regards,
Bean