[RFC PATCH v2 0/7] Add MMC packed request support

[Baolin Wang <baolin.wang7@gmail.com>]

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 extanded commit_rqs() to do batch processing suggested
by Ming, 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.

Changes from RFC v1:
 - Re-implement the batch processing according to Ming's suggestion
 - Remove the bd.last validation in MMC block.c, since we always get bd.last == false
 according to the new batch processing method.

Baolin Wang (6):
  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

Ming Lei (1):
  block: Extand commit_rqs() to do batch processing

 block/blk-mq-sched.c          |  29 +-
 block/blk-mq.c                |  15 +-
 drivers/mmc/core/block.c      |  14 +
 drivers/mmc/core/core.c       |  26 ++
 drivers/mmc/core/core.h       |   2 +
 drivers/mmc/core/queue.c      |  19 +-
 drivers/mmc/host/mmc_hsq.c    | 292 +++++++++++++++++---
 drivers/mmc/host/mmc_hsq.h    |  25 +-
 drivers/mmc/host/sdhci-sprd.c |  30 +-
 drivers/mmc/host/sdhci.c      | 504 +++++++++++++++++++++++++++++-----
 drivers/mmc/host/sdhci.h      |  61 +++-
 include/linux/blk-mq.h        |   1 +
 include/linux/mmc/core.h      |   6 +
 include/linux/mmc/host.h      |   9 +
 14 files changed, 900 insertions(+), 133 deletions(-)

-- 
2.17.1