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Subject: Re: Another approach of UFSHPB
To:     daejun7.park@samsung.com, yongmyung lee <ymhungry.lee@samsung.com>,
        Avri Altman <Avri.Altman@wdc.com>,
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        Zang Leigang <zangleigang@hisilicon.com>,
        Avi Shchislowski <Avi.Shchislowski@wdc.com>,
        Bean Huo <beanhuo@micron.com>,
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        MOHAMMED RAFIQ KAMAL BASHA <md.rafiq@samsung.com>,
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        Jinyoung CHOI <j-young.choi@samsung.com>,
        Adel Choi <adel.choi@samsung.com>,
        BoRam Shin <boram.shin@samsung.com>,
        Sung-Jun Park <sungjun07.park@samsung.com>
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From:   Bart Van Assche <bvanassche@acm.org>
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Date:   Mon, 25 May 2020 07:56:54 -0700
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On 2020-05-24 22:40, Daejun Park wrote:
> The HPB driver is close to the UFS core function, but it is not essential
> for operating UFS device. With reference to this article
> (https://lwn.net/Articles/645810/), we implemented extended UFS-feature
> as bus model. Because the HPB driver consumes the user's main memory, it should
> support bind / unbind functionality as needed. We implemented the HPB driver 
> can be unbind / unload on runtime.

I do not agree that the bus model is the best choice for freeing cache
memory if it is no longer needed. A shrinker is probably a much better
choice because the callback functions in a shrinker get invoked when a
system is under memory pressure. See also register_shrinker(),
unregister_shrinker() and struct shrinker in include/linux/shrinker.h.

>> Should these parameters be per module or per UFS device?
> 
> I think it is necessary to take parameters for each module. 
> This is because each extended UFS-feature module has different functions
> and may require different parameters.

My question was a rhetorical question. Please choose per device
parameters when appropriate instead of module parameters.

Thanks,

Bart.