Re: [PATCH v9 0/5] Add MMC software queue support

[Ulf Hansson]

On Wed, 12 Feb 2020 at 05:14, Baolin Wang <baolin.wang7@xxxxxxxxx> wrote:
>
> Hi All,
>
> Now the MMC read/write stack will always wait for previous request is
> completed by mmc_blk_rw_wait(), before sending a new request to hardware,
> or queue a work to complete request, that will bring context switching
> overhead, especially for high I/O per second rates, to affect the IO
> performance.
>
> Thus this patch set will introduce the MMC software command queue support
> based on command queue engine's interfaces, and set the queue depth as 64
> to allow more requests can be be prepared, merged and inserted into IO
> scheduler, but we only allow 2 requests in flight, that is enough to let
> the irq handler always trigger the next request without a context switch,
> as well as avoiding a long latency.
>
> Moreover we can expand the MMC software queue interface to support
> MMC packed request or packed command instead of adding new interfaces,
> according to previosus discussion.
>
> Below are some comparison data 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 in 4K block size.
>
> ./fio --filename=/dev/mmcblk0p30 --direct=1 --iodepth=20 --rw=read --bs=4K --size=1G --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. Without MMC software queue
> I tested 5 times for each case and output a average speed.
>
> 1) Sequential read:
> Speed: 59.4MiB/s, 63.4MiB/s, 57.5MiB/s, 57.2MiB/s, 60.8MiB/s
> Average speed: 59.66MiB/s
>
> 2) Random read:
> Speed: 26.9MiB/s, 26.9MiB/s, 27.1MiB/s, 27.1MiB/s, 27.2MiB/s
> Average speed: 27.04MiB/s
>
> 3) Sequential write:
> Speed: 71.6MiB/s, 72.5MiB/s, 72.2MiB/s, 64.6MiB/s, 67.5MiB/s
> Average speed: 69.68MiB/s
>
> 4) Random write:
> Speed: 36.3MiB/s, 35.4MiB/s, 38.6MiB/s, 34MiB/s, 35.5MiB/s
> Average speed: 35.96MiB/s
>
> 2. With MMC software queue
> I tested 5 times for each case and output a average speed.
>
> 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
>
> Form above data, we can see the MMC software queue can help to improve some
> performance obviously for random read and write, though no obvious improvement
> for sequential read and write.
>
> Any comments are welcome. Thanks a lot.
>
> Changes from v8:
>  - Add more description in the commit message.
>  - Optimize the failure log when calling cqe_enable().
>
> Changes from v7:
>  - Add reviewed tag from Arnd.
>  - Use the 'hsq' acronym for varibles and functions in the core layer.
>  - Check the 'card->ext_csd.cmdq_en' in cqhci.c to make sure the CQE
>  can work normally.
>  - Add a new patch to enable the host software queue for the SD card.
>  - Use the default MMC queue depth for host software queue.
>
> Changes from v6:
>  - Change the patch order and set host->always_defer_done = true for the
>  Spreadtrum host driver.
>
> Changes from v5:
>  - Modify the condition of defering to complete request suggested by Adrian.
>
> Changes from v4:
>  - Add a seperate patch to introduce a variable to defer to complete
>  data requests for some host drivers, when using host software queue.
>
> Changes from v3:
>  - Use host software queue instead of sqhci.
>  - Fix random config building issue.
>  - Change queue depth to 32, but still only allow 2 requests in flight.
>  - Update the testing data.
>
> Changes from v2:
>  - Remove reference to 'struct cqhci_host' and 'struct cqhci_slot',
>  instead adding 'struct sqhci_host', which is only used by software queue.
>
> Changes from v1:
>  - Add request_done ops for sdhci_ops.
>  - Replace virtual command queue with software queue for functions and
>  variables.
>  - Rename the software queue file and add sqhci.h header file.
>
> Baolin Wang (5):
>   mmc: Add MMC host software queue support
>   mmc: core: Enable the MMC host software queue for the SD card
>   mmc: host: sdhci: Add request_done ops for struct sdhci_ops
>   mmc: host: sdhci: Add a variable to defer to complete requests if
>     needed
>   mmc: host: sdhci-sprd: Add software queue support
>
>  drivers/mmc/core/block.c      |   61 ++++++++
>  drivers/mmc/core/mmc.c        |   18 ++-
>  drivers/mmc/core/queue.c      |   22 ++-
>  drivers/mmc/core/sd.c         |   10 ++
>  drivers/mmc/host/Kconfig      |    8 +
>  drivers/mmc/host/Makefile     |    1 +
>  drivers/mmc/host/cqhci.c      |    8 +-
>  drivers/mmc/host/mmc_hsq.c    |  343 +++++++++++++++++++++++++++++++++++++++++
>  drivers/mmc/host/mmc_hsq.h    |   30 ++++
>  drivers/mmc/host/sdhci-sprd.c |   28 ++++
>  drivers/mmc/host/sdhci.c      |   14 +-
>  drivers/mmc/host/sdhci.h      |    3 +
>  include/linux/mmc/host.h      |    3 +
>  13 files changed, 534 insertions(+), 15 deletions(-)
>  create mode 100644 drivers/mmc/host/mmc_hsq.c
>  create mode 100644 drivers/mmc/host/mmc_hsq.h
>
> --
> 1.7.9.5
>

Applied for next, thanks! Also, thanks for your patience while moving
forward during the reviews!

Note, I did some amending of patch1 to resolve some checkpatch
warnings. SPDX licence and Kconfig help texts, please have a look and
tell if there are something that doesn't look good.

Kind regards
Uffe