linux-kernel - RE: [PATCH v6 0/5] scsi: ufs: Add Host Performance Booster Support

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Date:   Wed, 15 Jul 2020 18:34:23 +0000
From:   Avi Shchislowski <Avi.Shchislowski@....com>
To:     "daejun7.park@...sung.com" <daejun7.park@...sung.com>,
        Avri Altman <Avri.Altman@....com>,
        "jejb@...ux.ibm.com" <jejb@...ux.ibm.com>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "asutoshd@...eaurora.org" <asutoshd@...eaurora.org>,
        "beanhuo@...ron.com" <beanhuo@...ron.com>,
        "stanley.chu@...iatek.com" <stanley.chu@...iatek.com>,
        "cang@...eaurora.org" <cang@...eaurora.org>,
        "bvanassche@....org" <bvanassche@....org>,
        "tomas.winkler@...el.com" <tomas.winkler@...el.com>,
        ALIM AKHTAR <alim.akhtar@...sung.com>
CC:     "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Sang-yoon Oh <sangyoon.oh@...sung.com>,
        Sung-Jun Park <sungjun07.park@...sung.com>,
        yongmyung lee <ymhungry.lee@...sung.com>,
        Jinyoung CHOI <j-young.choi@...sung.com>,
        Adel Choi <adel.choi@...sung.com>,
        BoRam Shin <boram.shin@...sung.com>
Subject: RE: [PATCH v6 0/5] scsi: ufs: Add Host Performance Booster Support

Hello All,
My name is Avi Shchislowski, I am managing the WDC's Linux Host R&D team in which Avri is a member of.
As the review process of HPB is progressing very constructively, we are getting more and more requests from OEMs, Inquiring about HPB in general, and host control mode in particular.

Their main concern is that HPB will make it to 5.9 merge window, but the host control mode patches will not.
Thus, because of recent Google's GKI, the next Android LTS might not include HPB with host control mode.

Aside of those requests, initial host control mode testing are showing promising prospective with respect of performance gain.

What would be, in your opinion, the best policy that host control mode is included in next Android LTS?

Thanks,
Avi

-----Original Message-----
From: linux-scsi-owner@...r.kernel.org <linux-scsi-owner@...r.kernel.org> On Behalf Of Daejun Park
Sent: Monday, July 13, 2020 1:34 PM
To: Avri Altman <Avri.Altman@....com>; jejb@...ux.ibm.com; martin.petersen@...cle.com; asutoshd@...eaurora.org; beanhuo@...ron.com; stanley.chu@...iatek.com; cang@...eaurora.org; bvanassche@....org; tomas.winkler@...el.com; ALIM AKHTAR <alim.akhtar@...sung.com>; Daejun Park <daejun7.park@...sung.com>
Cc: linux-scsi@...r.kernel.org; linux-kernel@...r.kernel.org; Sang-yoon Oh <sangyoon.oh@...sung.com>; Sung-Jun Park <sungjun07.park@...sung.com>; yongmyung lee <ymhungry.lee@...sung.com>; Jinyoung CHOI <j-young.choi@...sung.com>; Adel Choi <adel.choi@...sung.com>; BoRam Shin <boram.shin@...sung.com>
Subject: [PATCH v6 0/5] scsi: ufs: Add Host Performance Booster Support

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Changelog:

v5 -> v6
Change base commit to b53293fa662e28ae0cdd40828dc641c09f133405

v4 -> v5
Delete unused macro define.

v3 -> v4
1. Cleanup.

v2 -> v3
1. Add checking input module parameter value.
2. Change base commit from 5.8/scsi-queue to 5.9/scsi-queue.
3. Cleanup for unused variables and label.

v1 -> v2
1. Change the full boilerplate text to SPDX style.
2. Adopt dynamic allocation for sub-region data structure.
3. Cleanup.

NAND flash memory-based storage devices use Flash Translation Layer (FTL) to translate logical addresses of I/O requests to corresponding flash memory addresses. Mobile storage devices typically have RAM with constrained size, thus lack in memory to keep the whole mapping table.
Therefore, mapping tables are partially retrieved from NAND flash on demand, causing random-read performance degradation.

To improve random read performance, JESD220-3 (HPB v1.0) proposes HPB (Host Performance Booster) which uses host system memory as a cache for the FTL mapping table. By using HPB, FTL data can be read from host memory faster than from NAND flash memory.

The current version only supports the DCM (device control mode).
This patch consists of 4 parts to support HPB feature.

1) UFS-feature layer
2) HPB probe and initialization process
3) READ -> HPB READ using cached map information
4) L2P (logical to physical) map management

The UFS-feature is an additional layer to avoid the structure in which the UFS-core driver and the UFS-feature are entangled with each other in a single module.
By adding the layer, UFS-features composed of various combinations can be supported. Also, even if a new feature is added, modification of the UFS-core driver can be minimized.

In the HPB probe and init process, the device information of the UFS is queried. After checking supported features, the data structure for the HPB is initialized according to the device information.

A read I/O in the active sub-region where the map is cached is changed to HPB READ by the HPB module.

The HPB module manages the L2P map using information received from the device. For active sub-region, the HPB module caches through ufshpb_map request. For the in-active region, the HPB module discards the L2P map.
When a write I/O occurs in an active sub-region area, associated dirty bitmap checked as dirty for preventing stale read.

HPB is shown to have a performance improvement of 58 - 67% for random read workload. [1]

This series patches are based on the 5.9/scsi-queue branch.

[1]:
https://www.usenix.org/conference/hotstorage17/program/presentation/jeong

Daejun park (5):
 scsi: ufs: Add UFS feature related parameter
 scsi: ufs: Add UFS feature layer
 scsi: ufs: Introduce HPB module
 scsi: ufs: L2P map management for HPB read
 scsi: ufs: Prepare HPB read for cached sub-region

 drivers/scsi/ufs/Kconfig      |    9 +
 drivers/scsi/ufs/Makefile     |    3 +-
 drivers/scsi/ufs/ufs.h        |   12 +
 drivers/scsi/ufs/ufsfeature.c |  148 +++
 drivers/scsi/ufs/ufsfeature.h |   69 ++
 drivers/scsi/ufs/ufshcd.c     |   19 +
 drivers/scsi/ufs/ufshcd.h     |    2 +
 drivers/scsi/ufs/ufshpb.c     | 1997 ++++++++++++++++++++++++++++++++++++
 drivers/scsi/ufs/ufshpb.h     |  232 +++++
 9 files changed, 2490 insertions(+), 1 deletion(-)  created mode 100644 drivers/scsi/ufs/ufsfeature.c  created mode 100644 drivers/scsi/ufs/ufsfeature.h  created mode 100644 drivers/scsi/ufs/ufshpb.c  created mode 100644 drivers/scsi/ufs/ufshpb.h