linux-kernel - RE: [PATCH v2 5/5] scsi: ufs: UFS Host Performance Booster(HPB) driver

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Message-ID: <SN6PR04MB4640851C163648C54EB274C5FCD00@SN6PR04MB4640.namprd04.prod.outlook.com>
Date:   Fri, 24 Apr 2020 18:17:17 +0000
From:   Avri Altman <Avri.Altman@....com>
To:     Bart Van Assche <bvanassche@....org>,
        "huobean@...il.com" <huobean@...il.com>,
        "alim.akhtar@...sung.com" <alim.akhtar@...sung.com>,
        "asutoshd@...eaurora.org" <asutoshd@...eaurora.org>,
        "jejb@...ux.ibm.com" <jejb@...ux.ibm.com>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "stanley.chu@...iatek.com" <stanley.chu@...iatek.com>,
        "beanhuo@...ron.com" <beanhuo@...ron.com>,
        "tomas.winkler@...el.com" <tomas.winkler@...el.com>,
        "cang@...eaurora.org" <cang@...eaurora.org>
CC:     "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 5/5] scsi: ufs: UFS Host Performance Booster(HPB)
 driver

Hi Bart,

> What are the similarities and differences compared to the lightnvm
> framework that was added several years ago to the Linux kernel? Which of
> the code in this patch can be shared with the lightnvm framework?
Simply put, unlike lightnvn, HPB is not host-managed FTL, But instead can be perceived as a cost-reduction effort.
Its aim is not to move the fw to the host, but to control the iNAND cost by limiting the amount of its internal RAM.
It is done by using the host memory to cache the L2P tables, and replace READ_10 that have only the lba,
by an alternative command - HPB_READ, that have both the logical and physical addresses.

Using Lightnvm was considered in the past as possible framework for HPB, but was rejected by both Christoph & Mattias.

The HPB feature was NAKed by Christoph in its entirety, regardless of the driver design.
Until this is not reversed, keep commenting this patch is counterproductive and confusing.

Should this decision is reversed, I think this patch should be re-posted as a RFC,
And fragment its 5,000 lines or so into a set of reviewable patches.

Thanks,
Avri