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

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Date:   Mon, 12 Aug 2019 13:50:54 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Baolin Wang <baolin.wang@...aro.org>
Cc:     Jens Axboe <axboe@...nel.dk>, Ulf Hansson <ulf.hansson@...aro.org>,
        Chunyan Zhang <zhang.lyra@...il.com>,
        Orson Zhai <orsonzhai@...il.com>,
        Arnd Bergmann <arnd@...db.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        linux-mmc <linux-mmc@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, linux-block@...r.kernel.org
Subject: Re: [RFC PATCH 0/7] Add MMC packed function

On 12/08/19 12:44 PM, Baolin Wang wrote:
> Hi Adrian,
> 
> On Mon, 12 Aug 2019 at 16:59, Adrian Hunter <adrian.hunter@...el.com> wrote:
>>
>> On 12/08/19 8:20 AM, Baolin Wang wrote:
>>> Hi,
>>>
>>> On Mon, 22 Jul 2019 at 21:10, Baolin Wang <baolin.wang@...aro.org> 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.
> 

I meant did you consider using the CQE interface instead of creating another
one?