[PATCH v14 0/3] scsi: ufs: Add Host Performance Booster Support

[Daejun Park]

Changelog:

v13 -> v14
1. Cleanup codes by commentted in Greg's review.
2. Add documentation for sysfs entries (from Greg's review).
3. Add experiment result of HPB performance testing. (in this mail)

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.

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]

We measured the total start-up time of popular applications and observed
the difference by enabling the HPB.
Popular applications are 12 game apps and 24 non-game apps. Each target
applications were launched in order. The cycle consists of running 36
applications in sequence. We repeated the cycle for observing performance
improvement by L2P mapping cache hit in HPB.

The Following is experiment environment:
 - kernel version: 4.4.0 
 - UFS 2.1 (64GB)

Result:
+-------+----------+----------+-------+
| cycle | baseline | with HPB | diff  |
+-------+----------+----------+-------+
| 1     | 272.4    | 264.9    | -7.5  |
| 2     | 250.4    | 248.2    | -2.2  |
| 3     | 226.2    | 215.6    | -10.6 |
| 4     | 230.6    | 214.8    | -15.8 |
| 5     | 232.0    | 218.1    | -13.9 |
| 6     | 231.9    | 212.6    | -19.3 |
+-------+----------+----------+-------+

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

 Documentation/ABI/testing/sysfs-driver-ufs |   80 +
 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                  | 1767 ++++++++++++++++++++
 drivers/scsi/ufs/ufshpb.h                  |  230 +++
 9 files changed, 2229 insertions(+), 1 deletion(-)
 create mode 100644 drivers/scsi/ufs/ufshpb.c
 create mode 100644 drivers/scsi/ufs/ufshpb.h

--
2.25.1