[RFC PATCH 0/7] Add MMC packed function

[Baolin Wang]

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 patchset is
used to add the MMC packed function to support packed request or packed
command.

In this patch set, I 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.

./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
I tested 3 times for each case and output a average speed.

1) Sequential read:
Speed: 28.9MiB/s, 26.4MiB/s, 30.9MiB/s
Average speed: 28.7MiB/s

2) Random read:
Speed: 18.2MiB/s, 8.9MiB/s, 15.8MiB/s
Average speed: 14.3MiB/s

3) Sequential write:
Speed: 21.1MiB/s, 27.9MiB/s, 25MiB/s
Average speed: 24.7MiB/s

4) Random write:
Speed: 21.5MiB/s, 18.1MiB/s, 18.1MiB/s
Average speed: 19.2MiB/s

2. Packed request
In packed request mode, I set the host controller can package maximum 10
requests at one time (Actually I can increase the package number), and I
enabled read/write packed request mode. Also I tested 3 times for each
case and output a average speed.

1) Sequential read:
Speed: 165MiB/s, 167MiB/s, 164MiB/s
Average speed: 165.3MiB/s

2) Random read:
Speed: 147MiB/s, 141MiB/s, 144MiB/s
Average speed: 144MiB/s

3) Sequential write:
Speed: 87.8MiB/s, 89.1MiB/s, 90.0MiB/s
Average speed: 89MiB/s

4) Random write:
Speed: 90.9MiB/s, 89.8MiB/s, 90.4MiB/s
Average speed: 90.4MiB/s

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

Baolin Wang (7):
  blk-mq: Export blk_mq_hctx_has_pending() function
  mmc: core: Add MMC packed request function
  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/blk-mq.c                |    3 +-
 drivers/mmc/core/Kconfig      |    2 +
 drivers/mmc/core/Makefile     |    1 +
 drivers/mmc/core/block.c      |   71 +++++-
 drivers/mmc/core/block.h      |    3 +-
 drivers/mmc/core/core.c       |   51 ++++
 drivers/mmc/core/core.h       |    3 +
 drivers/mmc/core/packed.c     |  478 ++++++++++++++++++++++++++++++++++++++
 drivers/mmc/core/queue.c      |   28 ++-
 drivers/mmc/host/Kconfig      |    1 +
 drivers/mmc/host/sdhci-sprd.c |   22 +-
 drivers/mmc/host/sdhci.c      |  513 +++++++++++++++++++++++++++++++++++------
 drivers/mmc/host/sdhci.h      |   59 ++++-
 include/linux/blk-mq.h        |    1 +
 include/linux/mmc/core.h      |    1 +
 include/linux/mmc/host.h      |    3 +
 include/linux/mmc/packed.h    |  123 ++++++++++
 17 files changed, 1286 insertions(+), 77 deletions(-)
 create mode 100644 drivers/mmc/core/packed.c
 create mode 100644 include/linux/mmc/packed.h

-- 
1.7.9.5