[RFC PATCH 0/8] Add MMC packed request support

Baolin Wang
2020-01-17T05:25:12Z

Hi All,

Now some SD/MMC controllers can support packed command or packed request,
that means it can package multiple requests to host controller to be handled
at one time, which can improve the I/O performence. Thus this patch set
tries to add the MMC packed request function to support packed request or
packed command.

In this patch set, I changed the dispatch_request() interface to allow
dispatching a batch of requests to hardware and expanded the MMC software
queue to support packed request. I also implemented the SD host ADMA3
transfer mode to support packed request. The ADMA3 transfer mode can process
a multi-block data transfer by using a pair of command descriptor and ADMA2
descriptor. In future we can easily expand the MMC packed function to support
packed command.

Below are some comparison data between packed request and non-packed request
with fio tool. The fio command I used is like below with changing the
'--rw' parameter and enabling the direct IO flag to measure the actual hardware
transfer speed. I tested 5 times for each case and output a average speed.

./fio --filename=/dev/mmcblk0p30 --direct=1 --iodepth=20 --rw=read --bs=4K --size=512M --group_reporting --numjobs=20 --name=test_read

My eMMC card working at HS400 Enhanced strobe mode:
[ 2.229856] mmc0: new HS400 Enhanced strobe MMC card at address 0001
[ 2.237566] mmcblk0: mmc0:0001 HBG4a2 29.1 GiB
[ 2.242621] mmcblk0boot0: mmc0:0001 HBG4a2 partition 1 4.00 MiB
[ 2.249110] mmcblk0boot1: mmc0:0001 HBG4a2 partition 2 4.00 MiB
[ 2.255307] mmcblk0rpmb: mmc0:0001 HBG4a2 partition 3 4.00 MiB, chardev (248:0)

1. Non-packed request
1) Sequential read:
Speed: 59.2MiB/s, 60.4MiB/s, 63.6MiB/s, 60.3MiB/s, 59.9MiB/s
Average speed: 60.68MiB/s

2) Random read:
Speed: 31.3MiB/s, 31.4MiB/s, 31.5MiB/s, 31.3MiB/s, 31.3MiB/s
Average speed: 31.36MiB/s

3) Sequential write:
Speed: 71MiB/s, 71.8MiB/s, 72.3MiB/s, 72.2MiB/s, 71MiB/s
Average speed: 71.66MiB/s

4) Random write:
Speed: 68.9MiB/s, 68.7MiB/s, 68.8MiB/s, 68.6MiB/s, 68.8MiB/s
Average speed: 68.76MiB/s

2. Packed request
1) Sequential read:
Speed: 230MiB/s, 230MiB/s, 229MiB/s, 230MiB/s, 229MiB/s
Average speed: 229.6MiB/s

2) Random read:
Speed: 181MiB/s, 181MiB/s, 181MiB/s, 180MiB/s, 181MiB/s
Average speed: 180.8MiB/s

3) Sequential write:
Speed: 175MiB/s, 171MiB/s, 171MiB/s, 172MiB/s, 171MiB/s
Average speed: 172MiB/s

4) Random write:
Speed: 169MiB/s, 169MiB/s, 171MiB/s, 167MiB/s, 170MiB/s
Average speed: 169.2MiB/s

From above data, we can see the packed request can improve the performance
greatly. Any comments are welcome. Thanks a lot.

Baolin Wang (8):
block: Change the dispatch_request() API to support batch requests
block: Allow sending a batch of requests from the scheduler to
hardware
mmc: Add MMC packed request support for MMC software queue
mmc: host: sdhci: Introduce ADMA3 transfer mode
mmc: host: sdhci: Factor out the command configuration
mmc: host: sdhci: Remove redundant sg_count member of struct
sdhci_host
mmc: host: sdhci: Add MMC packed request support
mmc: host: sdhci-sprd: Add MMC packed request support

block/bfq-iosched.c | 38 +++-
block/blk-mq-sched.c | 15 +-
block/blk-mq.c | 2 -
block/blk-settings.c | 13 ++
block/kyber-iosched.c | 80 ++++---
block/mq-deadline.c | 26 ++-
drivers/mmc/core/block.c | 22 +-
drivers/mmc/core/block.h | 3 +-
drivers/mmc/core/core.c | 26 +++
drivers/mmc/core/core.h | 2 +
drivers/mmc/core/queue.c | 22 +-
drivers/mmc/host/mmc_hsq.c | 310 ++++++++++++++++++++++---
drivers/mmc/host/mmc_hsq.h | 26 ++-
drivers/mmc/host/sdhci-sprd.c | 30 ++-
drivers/mmc/host/sdhci.c | 499 +++++++++++++++++++++++++++++++++++------
drivers/mmc/host/sdhci.h | 61 ++++-
include/linux/blkdev.h | 8 +
include/linux/elevator.h | 2 +-
include/linux/mmc/core.h | 6 +
include/linux/mmc/host.h | 9 +
20 files changed, 1015 insertions(+), 185 deletions(-)

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1.7.9.5