[PATCH V8 00/20] mmc: mmc: Add Software Command Queuing

Adrian Hunter
2016-11-29T10:14:32Z

Hi

Here is an updated version of the Software Command Queuing patches,
re-based on next, with some changes - refer changes in V8 below.
It would be good to move at least a few of these patches: for example,
patches 2-7 could be considered to be tidy-ups. Patch 1 could be
rolled into the Packed Commands removal patch.

Performance results (not updated since V5):

Results can vary from run to run, but here are some results showing 1, 2 or 4
processes with 4k and 32k record sizes. They show up to 40% improvement in
read performance when there are multiple processes.

iozone -s 8192k -r 4k -i 0 -i 1 -i 2 -i 8 -I -t 1 -F /mnt/mmc/iozone1.tmp

Children see throughput for 1 initial writers = 27909.87 kB/sec 24204.14 kB/sec -13.28 %
Children see throughput for 1 rewriters = 28839.28 kB/sec 25531.92 kB/sec -11.47 %
Children see throughput for 1 readers = 25889.65 kB/sec 24883.23 kB/sec -3.89 %
Children see throughput for 1 re-readers = 25558.23 kB/sec 24679.89 kB/sec -3.44 %
Children see throughput for 1 random readers = 25571.48 kB/sec 24689.52 kB/sec -3.45 %
Children see throughput for 1 mixed workload = 25758.59 kB/sec 24487.52 kB/sec -4.93 %
Children see throughput for 1 random writers = 24787.51 kB/sec 19368.99 kB/sec -21.86 %

iozone -s 8192k -r 32k -i 0 -i 1 -i 2 -i 8 -I -t 1 -F /mnt/mmc/iozone1.tmp

Children see throughput for 1 initial writers = 91344.61 kB/sec 102008.56 kB/sec 11.67 %
Children see throughput for 1 rewriters = 87932.36 kB/sec 96630.44 kB/sec 9.89 %
Children see throughput for 1 readers = 134879.82 kB/sec 110292.79 kB/sec -18.23 %
Children see throughput for 1 re-readers = 147632.13 kB/sec 109053.33 kB/sec -26.13 %
Children see throughput for 1 random readers = 93547.37 kB/sec 112225.50 kB/sec 19.97 %
Children see throughput for 1 mixed workload = 93560.04 kB/sec 110515.21 kB/sec 18.12 %
Children see throughput for 1 random writers = 92841.84 kB/sec 81153.81 kB/sec -12.59 %

iozone -s 8192k -r 4k -i 0 -i 1 -i 2 -i 8 -I -t 2 -F /mnt/mmc/iozone1.tmp /mnt/mmc/iozone2.tmp

Children see throughput for 2 initial writers = 31145.43 kB/sec 33771.25 kB/sec 8.43 %
Children see throughput for 2 rewriters = 30592.57 kB/sec 35916.46 kB/sec 17.40 %
Children see throughput for 2 readers = 31669.83 kB/sec 37460.13 kB/sec 18.28 %
Children see throughput for 2 re-readers = 32079.94 kB/sec 37373.33 kB/sec 16.50 %
Children see throughput for 2 random readers = 27731.19 kB/sec 37601.65 kB/sec 35.59 %
Children see throughput for 2 mixed workload = 13927.50 kB/sec 14617.06 kB/sec 4.95 %
Children see throughput for 2 random writers = 31250.00 kB/sec 33106.72 kB/sec 5.94 %

iozone -s 8192k -r 32k -i 0 -i 1 -i 2 -i 8 -I -t 2 -F /mnt/mmc/iozone1.tmp /mnt/mmc/iozone2.tmp

Children see throughput for 2 initial writers = 123255.84 kB/sec 131252.22 kB/sec 6.49 %
Children see throughput for 2 rewriters = 115234.91 kB/sec 107225.74 kB/sec -6.95 %
Children see throughput for 2 readers = 128921.86 kB/sec 148562.71 kB/sec 15.23 %
Children see throughput for 2 re-readers = 127815.24 kB/sec 149304.32 kB/sec 16.81 %
Children see throughput for 2 random readers = 125600.46 kB/sec 148406.56 kB/sec 18.16 %
Children see throughput for 2 mixed workload = 44006.94 kB/sec 50937.36 kB/sec 15.75 %
Children see throughput for 2 random writers = 120623.95 kB/sec 103969.05 kB/sec -13.81 %

iozone -s 8192k -r 4k -i 0 -i 1 -i 2 -i 8 -I -t 4 -F /mnt/mmc/iozone1.tmp /mnt/mmc/iozone2.tmp /mnt/mmc/iozone3.tmp /mnt/mmc/iozone4.tmp

Children see throughput for 4 initial writers = 24100.96 kB/sec 33336.58 kB/sec 38.32 %
Children see throughput for 4 rewriters = 31650.20 kB/sec 33091.53 kB/sec 4.55 %
Children see throughput for 4 readers = 33276.92 kB/sec 41799.89 kB/sec 25.61 %
Children see throughput for 4 re-readers = 31786.96 kB/sec 41501.74 kB/sec 30.56 %
Children see throughput for 4 random readers = 31991.65 kB/sec 40973.93 kB/sec 28.08 %
Children see throughput for 4 mixed workload = 15804.80 kB/sec 13581.32 kB/sec -14.07 %
Children see throughput for 4 random writers = 31231.42 kB/sec 34537.03 kB/sec 10.58 %

iozone -s 8192k -r 32k -i 0 -i 1 -i 2 -i 8 -I -t 4 -F /mnt/mmc/iozone1.tmp /mnt/mmc/iozone2.tmp /mnt/mmc/iozone3.tmp /mnt/mmc/iozone4.tmp

Children see throughput for 4 initial writers = 116567.42 kB/sec 119280.35 kB/sec 2.33 %
Children see throughput for 4 rewriters = 115010.96 kB/sec 120864.34 kB/sec 5.09 %
Children see throughput for 4 readers = 130700.29 kB/sec 177834.21 kB/sec 36.06 %
Children see throughput for 4 re-readers = 125392.58 kB/sec 175975.28 kB/sec 40.34 %
Children see throughput for 4 random readers = 132194.57 kB/sec 176630.46 kB/sec 33.61 %
Children see throughput for 4 mixed workload = 56464.98 kB/sec 54140.61 kB/sec -4.12 %
Children see throughput for 4 random writers = 109128.36 kB/sec 85359.80 kB/sec -21.78 %

The current block driver supports 2 requests on the go at a time. Patches
3 - 8 make preparations for an arbitrary sized queue. Patches 9 - 12
introduce Command Queue definitions and helpers. Patches 13 - 16
complete the job of making the block driver use a queue. Patches 17 - 20
finally add Software Command Queuing. Most of the Software Command Queuing
functionality is added in patch 19.

As noted below, the patches can also be found here:

http://git.infradead.org/users/ahunter/linux-sdhci.git/shortlog/refs/heads/swcmdq

which also includes a debug-only patch to help debug stuck queues:
mmc: block: Add debugfs state file for debugging stuck queues

Changes in V8:

Re-based on next, dropping references to Packed Commands.

mmc: block: Restore line inadvertently removed with packed commands
New patch

mmc: block: Fix 4K native sector check
Moved to be the 2nd patch
Added Reviewed-by: Linus Walleij

mmc: queue: Fix queue thread wake-up
Added Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Added Reviewed-by: Harjani Ritesh <riteshh@codeaurora.org>

mmc: queue: Factor out mmc_queue_alloc_bounce_bufs()
Added Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Added Reviewed-by: Harjani Ritesh <riteshh@codeaurora.org>

mmc: queue: Factor out mmc_queue_alloc_bounce_sgs()
Added Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Added Reviewed-by: Harjani Ritesh <riteshh@codeaurora.org>

mmc: queue: Factor out mmc_queue_alloc_sgs()
Added Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Added Reviewed-by: Harjani Ritesh <riteshh@codeaurora.org>

mmc: queue: Factor out mmc_queue_reqs_free_bufs()
Added Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Added Reviewed-by: Harjani Ritesh <riteshh@codeaurora.org>

mmc: queue: Introduce queue depth
Drop chunk referring to mmc_packed_init().
Combined into new patch "mmc: queue: Introduce queue depth and use it to allocate and free"

mmc: queue: Use queue depth to allocate and free
Combined into new patch "mmc: queue: Introduce queue depth and use it to allocate and free"

mmc: queue: Allocate queue of size qdepth
Combined into new patch "mmc: queue: Introduce queue depth and use it to allocate and free"

mmc: queue: Introduce queue depth and use it to allocate and free
New patch from combining 3 patches above.

mmc: mmc: Add Command Queue definitions
Add comment about excluding qdepths of 1 or 2.

mmc: mmc: Add functions to enable / disable the Command Queue
Change mmc_cmdq_switch() 'enable' parameter from 'int' to 'bool'.

mmc: mmc_test: Disable Command Queue while mmc_test is used
Added Reviewed-by: Harjani Ritesh <riteshh@codeaurora.org>

mmc: block: Disable Command Queue while RPMB is used
As per Ritesh, assign 'ret' to 0 and return 'ret'.
Added Reviewed-by: Harjani Ritesh <riteshh@codeaurora.org>

mmc: core: Do not prepare a new request twice
Added Reviewed-by: Harjani Ritesh <riteshh@codeaurora.org>

mmc: core: Export mmc_retune_hold() and mmc_retune_release()
Added Reviewed-by: Harjani Ritesh <riteshh@codeaurora.org>

mmc: block: Factor out mmc_blk_requeue()
Dropped because it only affected "packed commands" code.

mmc: block: Use local var for mqrq_cur
Dropped chucks referring to Packed Commands.
Added Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

mmc: block: Pass mqrq to mmc_blk_prep_packed_list()
Dropped because it only affected "packed commands" code.

mmc: block: Introduce queue semantics
Add mmc_blk_requeue() lost from dropped patches.

mmc: queue: Share mmc request array between partitions
Dropped chucks referring to Packed Commands.
Change mqrq_ref_cnt from 'int' to 'unsigned int'
Add a comment about synchronisation of mqrq_ref_cnt.

mmc: mmc: Enable Software Command Queuing
Get rid of MMC_CAP_SWCMDQ and use MMC_CAP_CMD_DURING_TFR instead

mmc: sdhci-pci: Enable Software Command Queuing for some Intel controllers
Dropped because MMC_CAP_SWCMDQ removed.

mmc: sdhci-acpi: Enable Software Command Queuing for some Intel controllers
Dropped because MMC_CAP_SWCMDQ removed.

Changes in V7:

Re-based on next.

mmc: mmc: Add Command Queue definitions
Remove cmdq_en flag and add Linus Walleij's Reviewed-by.

mmc: mmc: Add functions to enable / disable the Command
Add cmdq_en flag.

Changes in V6:

mmc: core: Do not prepare a new request twice
Ensure struct mmc_async_req is always initialized to zero

Changes in V5:

Patches 1-5 dropped because they have been applied.

Re-based on next.

Fixed use of blk_end_request_cur() when it should have been
blk_end_request_all() to error out requests during error recovery.

Fixed unpaired retune_hold / retune_release in the error recovery path.

Changes in V4:

Re-based on next + v4.8-rc2 + "block: Fix secure erase" patch

Changes in V3:

Patches 1-25 dropped because they have been applied.

Re-based on next.

mmc: queue: Allocate queue of size qdepth
Free queue during cleanup

mmc: mmc: Add Command Queue definitions
Add cmdq_en to mmc-dev-attrs.txt documentation

mmc: queue: Share mmc request array between partitions
New patch

Changes in V2:

Added 5 patches already sent here:

http://marc.info/?l=linux-mmc&m=146712062816835

Added 3 more new patches:

mmc: sdhci-pci: Do not runtime suspend at the end of sdhci_pci_probe()
mmc: sdhci: Avoid STOP cmd triggering warning in sdhci_send_command()
mmc: sdhci: sdhci_execute_tuning() must delete timer

Carried forward the V2 fix to:

mmc: mmc_test: Disable Command Queue while mmc_test is used

Also reset the cmd circuit for data timeout if it is processing the data
cmd, in patch:

mmc: sdhci: Do not reset cmd or data circuits that are in use

There wasn't much comment on the RFC so there have been few changes.
Venu Byravarasu commented that it may be more efficient to use Software
Command Queuing only when there is more than 1 request queued - it isn't
obvious how well that would work in practice, but it could be added later
if it could be shown to be beneficial.

Original Cover Letter:

Chuanxiao Dong sent some patches last year relating to eMMC 5.1 Software
Command Queuing. He did not follow-up but I have contacted him and he says
it is OK if I take over upstreaming the patches.

eMMC Command Queuing is a feature added in version 5.1. The card maintains
a queue of up to 32 data transfers. Commands CMD45/CMD45 are sent to queue
up transfers in advance, and then one of the transfers is selected to
"execute" by CMD46/CMD47 at which point data transfer actually begins.

The advantage of command queuing is that the card can prepare for transfers
in advance. That makes a big difference in the case of random reads because
the card can start reading into its cache in advance.

A v5.1 host controller can manage the command queue itself, but it is also
possible for software to manage the queue using an non-v5.1 host controller
- that is what Software Command Queuing is.

Refer to the JEDEC (http://www.jedec.org/) eMMC v5.1 Specification for more
information about Command Queuing.

While these patches are heavily based on Dong's patches, there are some
changes:

SDHCI has been amended to support commands during transfer. That is a
generic change added in patches 1 - 5. [Those patches have now been applied]
In principle, that would also support SDIO's CMD52 during data transfer.

The original approach added multiple commands into the same request for
sending CMD44, CMD45 and CMD13. That is not strictly necessary and has
been omitted for now.

The original approach also called blk_end_request() from the mrq->done()
function, which means the upper layers learnt of completed requests
slightly earlier. That is not strictly related to Software Command Queuing
and is something that could potentially be done for all data requests.
That has been omitted for now.

The current block driver supports 2 requests on the go at a time. Patches
1 - 8 make preparations for an arbitrary sized queue. Patches 9 - 12
introduce Command Queue definitions and helpers. Patches 13 - 19
complete the job of making the block driver use a queue. Patches 20 - 23
finally add Software Command Queuing, and 24 - 25 enable it for Intel eMMC
controllers. Most of the Software Command Queuing functionality is added
in patch 22.

The patches can also be found here:

http://git.infradead.org/users/ahunter/linux-sdhci.git/shortlog/refs/heads/swcmdq

The patches have only had basic testing so far. Ad-hoc testing shows a
degradation in sequential read performance of about 10% but an increase in
throughput for mixed workload of multiple processes of about 90%. The
reduction in sequential performance is due to the need to read the Queue
Status register between each transfer.

These patches should not conflict with Hardware Command Queuing which
handles the queue in a completely different way and thus does not need
to share code with Software Command Queuing. The exceptions being the
Command Queue definitions and queue allocation which should be able to be
used.

Adrian Hunter (20):
mmc: block: Restore line inadvertently removed with packed commands
mmc: block: Fix 4K native sector check
mmc: queue: Fix queue thread wake-up
mmc: queue: Factor out mmc_queue_alloc_bounce_bufs()
mmc: queue: Factor out mmc_queue_alloc_bounce_sgs()
mmc: queue: Factor out mmc_queue_alloc_sgs()
mmc: queue: Factor out mmc_queue_reqs_free_bufs()
mmc: queue: Introduce queue depth and use it to allocate and free
mmc: mmc: Add Command Queue definitions
mmc: mmc: Add functions to enable / disable the Command Queue
mmc: mmc_test: Disable Command Queue while mmc_test is used
mmc: block: Disable Command Queue while RPMB is used
mmc: core: Do not prepare a new request twice
mmc: core: Export mmc_retune_hold() and mmc_retune_release()
mmc: block: Use local var for mqrq_cur
mmc: block: Introduce queue semantics
mmc: queue: Share mmc request array between partitions
mmc: queue: Add a function to control wake-up on new requests
mmc: block: Add Software Command Queuing
mmc: mmc: Enable Software Command Queuing

Documentation/mmc/mmc-dev-attrs.txt | 1 +
drivers/mmc/card/block.c | 712 +++++++++++++++++++++++++++++++++---
drivers/mmc/card/mmc_test.c | 21 +-
drivers/mmc/card/queue.c | 328 +++++++++++------
drivers/mmc/card/queue.h | 27 +-
drivers/mmc/core/core.c | 18 +-
drivers/mmc/core/host.c | 2 +
drivers/mmc/core/host.h | 2 -
drivers/mmc/core/mmc.c | 44 ++-
drivers/mmc/core/mmc_ops.c | 28 ++
include/linux/mmc/card.h | 8 +
include/linux/mmc/core.h | 6 +
include/linux/mmc/host.h | 3 +-
include/linux/mmc/mmc.h | 17 +
14 files changed, 1035 insertions(+), 182 deletions(-)

Regards
Adrian