Re: [RFC PATCH 0/5] scsi: ufs: Add Host Performance Booster Support

[Bean Huo]

Hi Daejun

Nice to see your patch, I just run it on my testing workspace, work.
and in the next days, I can help you review your patch.

Thanks,
Bean
 

On Fri, 2020-06-05 at 10:16 +0900, Daejun Park wrote:
> 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, we propose 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 "5.8/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      |    8 +
>  drivers/scsi/ufs/Makefile     |    3 +-
>  drivers/scsi/ufs/ufs.h        |   11 +
>  drivers/scsi/ufs/ufsfeature.c |  178 ++++
>  drivers/scsi/ufs/ufsfeature.h |   95 ++
>  drivers/scsi/ufs/ufshcd.c     |   19 +
>  drivers/scsi/ufs/ufshcd.h     |    3 +
>  drivers/scsi/ufs/ufshpb.c     | 2029
> +++++++++++++++++++++++++++++++++++++++++
>  drivers/scsi/ufs/ufshpb.h     |  257 ++++++
>  9 files changed, 2602 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