linux-kernel - RE: [PATCH] scsi: ufs: Optimize the WB flush process to save device power consumption

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Date:   Wed, 28 Jun 2023 11:00:40 +0000
From:   Avri Altman <Avri.Altman@....com>
To:     Lu Hongfei <luhongfei@...o.com>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Bart Van Assche <bvanassche@....org>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Bean Huo <beanhuo@...ron.com>,
        Asutosh Das <quic_asutoshd@...cinc.com>,
        "Bao D. Nguyen" <quic_nguyenb@...cinc.com>,
        Keoseong Park <keosung.park@...sung.com>,
        Arthur Simchaev <Arthur.Simchaev@....com>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "opensource.kernel@...o.com" <opensource.kernel@...o.com>,
        Tang Huan <tanghuan@...o.com>
Subject: RE: [PATCH] scsi: ufs: Optimize the WB flush process to save device
 power consumption

> 
> In the original logic, WB Hibern Flush was always on.
> During suspend flow, the host will determine whether the device needs
> BKOP or WB flush, and if so, it will keep VCC supply.
> WB flush is only a part of BKOP, and device that needs BKOP do not
> necessarily need WB flush if the conditions are not met. Therefore,
> if WB flush is not needed, it will be better to disable WB Hibern
> Flush,..... 
I beg to differ on this conclusion.
If you expect SLC write performance, without fluctuations,
the host should let the device manage its wb buffer on its own.
This is exactly what flush on hibernate does and better leave it be.

Thanks,
Avri