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

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Date:   Mon, 12 Aug 2019 11:58:00 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Baolin Wang <baolin.wang@...aro.org>, Jens Axboe <axboe@...nel.dk>,
        Ulf Hansson <ulf.hansson@...aro.org>
Cc:     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 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?

>>
>> 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?