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

Message ID cover.1587888520.git.baolin.wang7@gmail.com
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  • Add MMC packed request support
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Baolin Wang April 26, 2020, 9:38 a.m.
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