linux-kernel - RE: [RESENT PATCH RFC v3 5/5] scsi: ufs: UFS Host Performance Booster(HPB) driver

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Message-ID: <BYAPR04MB462904DA704A8FD42436BA9FFCA20@BYAPR04MB4629.namprd04.prod.outlook.com>
Date:   Fri, 8 May 2020 11:38:31 +0000
From:   Avri Altman <Avri.Altman@....com>
To:     "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>,
        "bvanassche@....org" <bvanassche@....org>,
        "tomas.winkler@...el.com" <tomas.winkler@...el.com>,
        "cang@...eaurora.org" <cang@...eaurora.org>,
        "rdunlap@...radead.org" <rdunlap@...radead.org>
CC:     "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "hch@...radead.org" <hch@...radead.org>
Subject: RE: [RESENT PATCH RFC v3 5/5] scsi: ufs: UFS Host Performance
 Booster(HPB) driver

Hi Bean,
This patch is ~3,000 lines long.
Is it possible to divide it into a series of a smaller, more reviewable patches?
E.g. it can be something like:
1) Init part I - Read HPB config
2) Init part II - prepare for L2P cache management (introduce here all the new data structures, memory allocation, etc.)
3) L2P cache management - activation / inactivation / eviction handlers
4) Add response API
5) Add prep_fn handler - the flows that contruct HPB-READ command.
Or any other division that makes sense to you.

Also, Is there a way to avoid all those #ifdefs everywhere?

Thanks,
Avri

 
> 
> From: Bean Huo <beanhuo@...ron.com>
> 
> This patch is to add support for the UFS Host Performance Booster (HPB
> v1.0),
> which is used to improve UFS read performance, especially for the random
> read.
> 
> NAND flash-based storage devices, including UFS, have mechanisms to
> translate
> logical addresses of requests to the corresponding physical addresses of the
> flash storage. Traditionally this L2P mapping data is loaded to the internal
> SRAM in the storage controller. When the capacity of storage is larger, a
> larger size of SRAM for the L2P map data is required. Since increased SRAM
> size affects the manufacturing cost significantly, it is not cost-effective
> to allocate all the amount of SRAM needed to keep all the Logical-address to
> Physical-address (L2P) map data. Therefore, L2P map data, which is required
> to identify the physical address for the requested IOs, can only be partially
> stored in SRAM from NAND flash. Due to this partial loading, accessing the
> flash address area where the L2P information for that address is not loaded
> in the SRAM can result in serious performance degradation.
> 
> The HPB is a software solution for the above problem, which uses the host’s
> system memory as a cache for the FTL L2P mapping table. It does not need
> additional hardware support from the host side. By using HPB, the L2P
> mapping
> table can be read from host memory and stored in host-side memory. while
> reading the operation, the corresponding L2P information will be sent to the
> UFS device along with the reading request. Since the L2P entry is provided in
> the read request, UFS device does not have to load L2P entry from flash
> memory.
> This will significantly improve random read performance.
> 
> Signed-off-by: Bean Huo <beanhuo@...ron.com>
> ---
>  drivers/scsi/ufs/Kconfig  |   62 +
>  drivers/scsi/ufs/Makefile |    1 +
>  drivers/scsi/ufs/ufshcd.c |  234 +++-
>  drivers/scsi/ufs/ufshcd.h |   23 +
>  drivers/scsi/ufs/ufshpb.c | 2767
> +++++++++++++++++++++++++++++++++++++
>  drivers/scsi/ufs/ufshpb.h |  423 ++++++
>  6 files changed, 3504 insertions(+), 6 deletions(-)
>  create mode 100644 drivers/scsi/ufs/ufshpb.c
>  create mode 100644 drivers/scsi/ufs/ufshpb.h
>