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Date:   Thu, 05 Nov 2020 16:16:51 +0800
From:   Can Guo <cang@codeaurora.org>
To:     daejun7.park@samsung.com
Cc:     avri.altman@wdc.com, jejb@linux.ibm.com,
        martin.petersen@oracle.com, asutoshd@codeaurora.org,
        beanhuo@micron.com, stanley.chu@mediatek.com, bvanassche@acm.org,
        tomas.winkler@intel.com, ALIM AKHTAR <alim.akhtar@samsung.com>,
        gregkh@google.com, linux-scsi@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Sang-yoon Oh <sangyoon.oh@samsung.com>,
        Sung-Jun Park <sungjun07.park@samsung.com>,
        yongmyung lee <ymhungry.lee@samsung.com>,
        Jinyoung CHOI <j-young.choi@samsung.com>,
        Adel Choi <adel.choi@samsung.com>,
        BoRam Shin <boram.shin@samsung.com>,
        SEUNGUK SHIN <seunguk.shin@samsung.com>
Subject: Re: [PATCH v13 0/3] scsi: ufs: Add Host Performance Booster Support
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On 2020-11-03 12:40, Daejun Park wrote:
> Changelog:
> 
> v12 -> v13
> 1. Cleanup codes by comments from Can Guo.
> 2. Add HPB related descriptor/flag/attributes in sysfs.
> 3. Change base commit from 5.10/scsi-queue to 5.11/scsi-queue.
> 

If you have changed the code based by comments left on Google gerrit, 
here is

Reviewed-by: Can Guo <cang@codeaurora.org>

> v11 -> v12
> 1. Fixed to return error value when HPB fails to initialize pinned 
> active
> region.
> 2. Fixed to disable HPB feature if HPB fails to allocate essential 
> memory
> and workqueue.
> 3. Fixed to change proper sub-region state when region is already 
> evicted.
> 
> v10 -> v11
> Add a newline at end the last line on Kconfig file.
> 
> v9 -> v10
> 1. Fixed 64-bit division error
> 2. Fixed problems commentted in Bart's review.
> 
> v8 -> v9
> 1. Change sysfs initialization.
> 2. Change reading descriptor during HPB initialization
> 3. Fixed problems commentted in Bart's review.
> 4. Change base commit from 5.9/scsi-queue to 5.10/scsi-queue.
> 
> v7 -> v8
> Remove wrongly added tags.
> 
> v6 -> v7
> 1. Remove UFS feature layer.
> 2. Cleanup for sparse error.
> 
> 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 3 parts to support HPB feature.
> 
> 1) HPB probe and initialization process
> 2) READ -> HPB READ using cached map information
> 3) L2P (logical to physical) map management
> 
> 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.
> 
> The HPB manages the L2P map using information received from the
> device. For active sub-region, the HPB caches through ufshpb_map
> request. For the in-active region, the HPB 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 5.11/scsi-queue branch.
> 
> [1]:
> https://www.usenix.org/conference/hotstorage17/program/presentation/jeong
> 
> Daejun park (3):
>  scsi: ufs: Introduce HPB feature
>  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    |    1 +
>  drivers/scsi/ufs/ufs-sysfs.c |   18 +
>  drivers/scsi/ufs/ufs.h       |   49 +
>  drivers/scsi/ufs/ufshcd.c    |   53 ++
>  drivers/scsi/ufs/ufshcd.h    |   23 +-
>  drivers/scsi/ufs/ufshpb.c    | 1784 
> +++++++++++++++++++++++++++++++++++++
>  drivers/scsi/ufs/ufshpb.h    |  230 +++++
>  8 files changed, 2166 insertions(+), 1 deletion(-)
>  created mode 100644 drivers/scsi/ufs/ufshpb.c
>  created mode 100644 drivers/scsi/ufs/ufshpb.h