[PATCH v9 0/2] mmc: support packed command feature of eMMC4.5

[PATCH v9 0/2] mmc: support packed command feature of eMMC4.5

[Seungwon Jeon]

This patch-set adds support of packed command feature for eMMC4.5 devices.
Specially, packed write is introduced.

Seeing the NAND flash, write is expensive operation including the block management internally.
Because write data cannot be overwritten on the NAND cell, additional operation is needed.
Overhead of the management can be reduced with once large write size rather than several data of small size.
That is when writing large amounts of data, eMMC gives a significant speed advantage.
Packed write can help it by gathering the data. Actually we got the performance gain.
For experiments, three eMMCs of different type from two vendor are used.

Additionally, there is a interesting result for packed read.
Packed read has been excluded from whole patch-set with a performance regression conclusively.
I found the reason for this regression. As we know, asynchronous transfer improves the performance
over than 20% for the read.  And I found that packed read actually gives performance gain of 2% 
only if asynchronous transfer is disabled. This shows that asynchronous transfer is more effective 
than packed read although packed read is a bit useful.

When several requests is packed for read, asynchronous transfer doesn't occur. That is packed read replaces
asynchronous transfer. Choice of packed read equals to the abandonment of asynchronous transfer.
This also means the abandonment of performance advantage. As a result, asynchronous transfer is currently
best choice regarding the read.

Changes in v9:
	- Rebase with the latest mmc.
	- Rework including reconstitution of data struct, on the whole.
	* Extend the number of blocks for packed header considering large sector (according to the eMMC 4.51)
	* Use flag of mmc_blk_data to identify permission of packed command.
	* Check the max commands strictly conforming to mandatory minimum values of spec.
	Note: These patch-set is dependant in the following patch.
	[PATCH 2/2] mmc: block: don't start new request when the card is removed
	
Changes in v8:
	- Ensure the alignment of sector size for native 4KB sector
	  in command packing(from Subhash Jadavani)
	- Exclude packed read in this phase due to performance issue.

Changes in v7:
	- Break the endless execution in some error handling(from Maya Erez).
	- Change the condition for enabling packed command(from Subhash Jadavani).
	- Spilt the error related routine from mmc_blk_issue_rw_rq.

Changes in v6:
	- Split the patch for packed read.
	- Remove the unnecessary code. 

Changes in v5:
	- Revert "Add a variable member in mmc_host for minimum number of packed entries".
	- Fix the partial packed command from failure index.
	- Clean an unnecessary parameter of mmc_blk_packed_hdr_wrq_prep 
	- Clean warning of checkpatch.

Changes in v4:
	- Add Data-tag as CMD23 argument for packed header.
	- Separate the capability of MMC_CAP2_PACKED_CMD into read and write.
	- Remove unncessary initial value.

Changes in v3:
	- Add a variable member in mmc_host for minimum number of packed entries.
	  This value can be overridden by host.
	- Fix a handling of error sequence.

Changes in v2:
	- Fix the packed read sequence and error handling.
	- Apply checking the exception status for all cases with
	  the comments from Maya Erez and Sahitya Tummala.
	- Fix preparing the packed list with the comment from Maya Erez and Venkatraman.

Seungwon Jeon (2):
      mmc: add packed command feature of eMMC4.5
      mmc: support packed write command for eMMC4.5 device
	
drivers/mmc/card/block.c   |  454 ++++++++++++++++++++++++++++++++++++++++++--
drivers/mmc/card/queue.c   |   96 +++++++++-
drivers/mmc/card/queue.h   |   22 ++
drivers/mmc/core/mmc.c     |   28 +++
drivers/mmc/core/mmc_ops.c |    1 +
include/linux/mmc/card.h   |    8 +
include/linux/mmc/core.h   |    4 +
include/linux/mmc/host.h   |    9 +
include/linux/mmc/mmc.h    |   15 ++-
9 files changed, 618 insertions(+), 19 deletions(-)

Thanks,
Seungwon Jeon
--
1.7.2.3

Re: [PATCH v9 0/2] mmc: support packed command feature of eMMC4.5

[merez]

Hi Seungwon Jeon,

Your findings on the packed reads are very interesting. Thanks for sharing.

Regarding the write packing:
We tested the write packing feature on 4 different card vendors with
msm_sdcc controller, using the following benchmarks:
tiotest seq: 	tiotest -t 1 -d /data -f 800 -b $((512*1024)) -k 1 -k 3
tiotest rand:	tiotest -t 4 -d /data -f 800 -b 4096 -k 2 -k 0 -p -s 2012 -r
12500 -n 20
lmdd write: lmdd if=internal of=/data/push1 bs=128k count=2000 sync=1
iozone (many flushes): iozone -i0 -i2 -r4k –s100m -O -o -I -f /data/file3
iozone:	iozone -i0 -i2 -r4k –s100m -O -I -f /data/file3

Our conclusions are as follows:
- In case the card supports write packing in API level only, there is no
improvement
- Some of cards benefit from the write packing for sequential scenarios
(~30% improvement)
- Some of the cards benefit from the write packing for random scenarios
(with tiotest we could even see doubling the performance with write
packing)

All the above tests were performed with HS-200.

The results were collected using the previous version of the patch.
I have a very busy week and I’m not sure I will be able to test the new
version of the patch. I will make an effort to test it as soon as I have
some free time.

Thanks,
Maya

> This patch-set adds support of packed command feature for eMMC4.5 devices.
> Specially, packed write is introduced.
>
> Seeing the NAND flash, write is expensive operation including the block
> management internally.
> Because write data cannot be overwritten on the NAND cell, additional
> operation is needed.
> Overhead of the management can be reduced with once large write size
> rather than several data of small size.
> That is when writing large amounts of data, eMMC gives a significant speed
> advantage.
> Packed write can help it by gathering the data. Actually we got the
> performance gain.
> For experiments, three eMMCs of different type from two vendor are used.
>
> Additionally, there is a interesting result for packed read.
> Packed read has been excluded from whole patch-set with a performance
> regression conclusively.
> I found the reason for this regression. As we know, asynchronous transfer
> improves the performance
> over than 20% for the read.  And I found that packed read actually gives
> performance gain of 2%
> only if asynchronous transfer is disabled. This shows that asynchronous
> transfer is more effective
> than packed read although packed read is a bit useful.
>
> When several requests is packed for read, asynchronous transfer doesn't
> occur. That is packed read replaces
> asynchronous transfer. Choice of packed read equals to the abandonment of
> asynchronous transfer.
> This also means the abandonment of performance advantage. As a result,
> asynchronous transfer is currently
> best choice regarding the read.
>
> Changes in v9:
> 	- Rebase with the latest mmc.
> 	- Rework including reconstitution of data struct, on the whole.
> 	* Extend the number of blocks for packed header considering large sector
> (according to the eMMC 4.51)
> 	* Use flag of mmc_blk_data to identify permission of packed command.
> 	* Check the max commands strictly conforming to mandatory minimum values
> of spec.
> 	Note: These patch-set is dependant in the following patch.
> 	[PATCH 2/2] mmc: block: don't start new request when the card is removed
>
> Changes in v8:
> 	- Ensure the alignment of sector size for native 4KB sector
> 	  in command packing(from Subhash Jadavani)
> 	- Exclude packed read in this phase due to performance issue.
>
> Changes in v7:
> 	- Break the endless execution in some error handling(from Maya Erez).
> 	- Change the condition for enabling packed command(from Subhash
> Jadavani).
> 	- Spilt the error related routine from mmc_blk_issue_rw_rq.
>
> Changes in v6:
> 	- Split the patch for packed read.
> 	- Remove the unnecessary code.
>
> Changes in v5:
> 	- Revert "Add a variable member in mmc_host for minimum number of packed
> entries".
> 	- Fix the partial packed command from failure index.
> 	- Clean an unnecessary parameter of mmc_blk_packed_hdr_wrq_prep
> 	- Clean warning of checkpatch.
>
> Changes in v4:
> 	- Add Data-tag as CMD23 argument for packed header.
> 	- Separate the capability of MMC_CAP2_PACKED_CMD into read and write.
> 	- Remove unncessary initial value.
>
> Changes in v3:
> 	- Add a variable member in mmc_host for minimum number of packed entries.
> 	  This value can be overridden by host.
> 	- Fix a handling of error sequence.
>
> Changes in v2:
> 	- Fix the packed read sequence and error handling.
> 	- Apply checking the exception status for all cases with
> 	  the comments from Maya Erez and Sahitya Tummala.
> 	- Fix preparing the packed list with the comment from Maya Erez and
> Venkatraman.
>
> Seungwon Jeon (2):
>       mmc: add packed command feature of eMMC4.5
>       mmc: support packed write command for eMMC4.5 device
>
> drivers/mmc/card/block.c   |  454
> ++++++++++++++++++++++++++++++++++++++++++--
> drivers/mmc/card/queue.c   |   96 +++++++++-
> drivers/mmc/card/queue.h   |   22 ++
> drivers/mmc/core/mmc.c     |   28 +++
> drivers/mmc/core/mmc_ops.c |    1 +
> include/linux/mmc/card.h   |    8 +
> include/linux/mmc/core.h   |    4 +
> include/linux/mmc/host.h   |    9 +
> include/linux/mmc/mmc.h    |   15 ++-
> 9 files changed, 618 insertions(+), 19 deletions(-)
>
> Thanks,
> Seungwon Jeon
> --
> 1.7.2.3
>
>
>


-- 
Maya Erez
QUALCOMM ISRAEL, on behalf of Qualcomm Innovation Center, Inc. is a member
of Code Aurora Forum, hosted by The Linux Foundation

Re: [PATCH v9 0/2] mmc: support packed command feature of eMMC4.5

[Chris Ball]

Hi Seungwon,

On Wed, Feb 06 2013, Seungwon Jeon wrote:
> This patch-set adds support of packed command feature for eMMC4.5 devices.
> Specially, packed write is introduced.

Thanks, I've pushed this to mmc-next for 3.9 now.

It would be great to see benchmarks for the effect on average write
latency, instead of just throughput, though.

- Chris.
-- 
Chris Ball   <cjb@laptop.org>   <http://printf.net/>
One Laptop Per Child

Re: [PATCH v9 0/2] mmc: support packed command feature of eMMC4.5

[Arnd Bergmann]

On Monday 11 February 2013, Chris Ball wrote:
> On Wed, Feb 06 2013, Seungwon Jeon wrote:
> > This patch-set adds support of packed command feature for eMMC4.5 devices.
> > Specially, packed write is introduced.
> 
> Thanks, I've pushed this to mmc-next for 3.9 now.
> 
> It would be great to see benchmarks for the effect on average write
> latency, instead of just throughput, though.

Yes, I agree absolutely. In the end, it's always the latency that
matters for user experience not the maximum throughput.

	Arnd

RE: [PATCH v9 0/2] mmc: support packed command feature of eMMC4.5

[Seungwon Jeon]

On Tuesday, February 12, 2013, Arnd Bergmann wrote:
> On Monday 11 February 2013, Chris Ball wrote:
> > On Wed, Feb 06 2013, Seungwon Jeon wrote:
> > > This patch-set adds support of packed command feature for eMMC4.5 devices.
> > > Specially, packed write is introduced.
> >
> > Thanks, I've pushed this to mmc-next for 3.9 now.
> >
> > It would be great to see benchmarks for the effect on average write
> > latency, instead of just throughput, though.
> 
> Yes, I agree absolutely. In the end, it's always the latency that
> matters for user experience not the maximum throughput.
I didn't see a significant difference in random I/O.
Write packing completely depends on seamless I/O from block layer.
As size of media contents is bigger, enhanced write is required in some user scenarios.
I guess write throughput is important factor cannot be easily ignored.

Thanks,
Seungwon Jeon
> 
> 	Arnd
> --
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Re: [PATCH v9 0/2] mmc: support packed command feature of eMMC4.5

[merez]