Re: [RFC PATCH 0/7] Add MMC packed function

[Baolin Wang]

Hi Adrian,

On Mon, 12 Aug 2019 at 16:59, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote:
>
> On 12/08/19 8:20 AM, Baolin Wang wrote:
> > Hi,
> >
> > On Mon, 22 Jul 2019 at 21:10, Baolin Wang <baolin.wang@xxxxxxxxxx> wrote:
> >>
> >> 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
>
> This seems surprising low for a HS400ES card.  Do you know why that is?

I've set the clock to 400M, but it seems the hardware did not output
the corresponding clock. I will check my hardware.

> >>
> >> 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.
> >
> > Any comments for this patch set? Thanks.
>
> Did you consider adapting the CQE interface?

I am not very familiar with CQE, since my controller did not support
it. But the MMC packed function had introduced some callbacks to help
for different controllers to do packed request, so I think it is easy
to adapt the CQE interface.

-- 
Baolin Wang
Best Regards