Hi Philip..

I have something question..did you test SDMA and ADMA?

Actually i didn't test [patch v3] but i tested patch v2 before Per sent.
I got that SDMA is faster than ADMA. (using bounce buffer and sdhci)

How do you think about that? I want to know your thought.
And if you can share the results, i want to know them.

Regards,
Jaehoon Chung


Philip Rakity wrote:

On May 9, 2011, at 5:34 AM, Per Forlin wrote:

quoted

On 9 May 2011 04:05, Philip Rakity [off-list ref] wrote:

quoted

Hi Per,

We noticed on some of our systems if we ADMA or SDMA and a bounce buffer it is significantly faster then SDMA.

I have not done work with ADMA or SDMA. Where should I look to read
more about it?
Are these the right places. DMA iop-dma.c and imx-sdma.c, MMC: sdhci.c.

sdhci.c for ADMA and SDMA

spec is at
http://www.sdcard.org/developers/tech/sdcard/pls/simplified_specs/

version 3 discusses ADMA

quoted

quoted

I believe ADMA will do large transfers.  Another data point.

Philip

Thanks,
Per

quoted

On May 7, 2011, at 12:14 PM, Per Forlin wrote:

quoted

How significant is the cache maintenance over head?
It depends, the eMMC are much faster now
compared to a few years ago and cache maintenance cost more due to
multiple cache levels and speculative cache pre-fetch. In relation the
cost for handling the caches have increased and is now a bottle neck
dealing with fast eMMC together with DMA.

The intention for introducing none blocking mmc requests is to minimize the
time between a mmc request ends and another mmc request starts. In the
current implementation the MMC controller is idle when dma_map_sg and
dma_unmap_sg is processing. Introducing none blocking mmc request makes it
possible to prepare the caches for next job parallel with an active
mmc request.

This is done by making the issue_rw_rq() none blocking.
The increase in throughput is proportional to the time it takes to
prepare (major part of preparations is dma_map_sg and dma_unmap_sg)
a request and how fast the memory is. The faster the MMC/SD is
the more significant the prepare request time becomes. Measurements on U5500
and Panda on eMMC and SD shows significant performance gain for for large
reads when running DMA mode. In the PIO case the performance is unchanged.

There are two optional hooks pre_req() and post_req() that the host driver
may implement in order to move work to before and after the actual mmc_request
function is called. In the DMA case pre_req() may do dma_map_sg() and prepare
the dma descriptor and post_req runs the dma_unmap_sg.

Details on measurements from IOZone and mmc_test:
https://wiki.linaro.org/WorkingGroups/Kernel/Specs/StoragePerfMMC-async-req

Under consideration:
* Make pre_req and post_req private to core.c.
* Generalize implementation and make it available for SDIO.

Changes since v2:
* Fix compile warnings in core.c and block.c
* Simplify max transfer size in mmc_test
* set TASK_RUNNING in queue.c before issue_req()

Per Forlin (12):
 mmc: add none blocking mmc request function
 mmc: mmc_test: add debugfs file to list all tests
 mmc: mmc_test: add test for none blocking transfers
 mmc: add member in mmc queue struct to hold request data
 mmc: add a block request prepare function
 mmc: move error code in mmc_block_issue_rw_rq to a separate function.
 mmc: add a second mmc queue request member
 mmc: add handling for two parallel block requests in issue_rw_rq
 mmc: test: add random fault injection in core.c
 omap_hsmmc: use original sg_len for dma_unmap_sg
 omap_hsmmc: add support for pre_req and post_req
 mmci: implement pre_req() and post_req()

drivers/mmc/card/block.c      |  493 +++++++++++++++++++++++++++--------------
drivers/mmc/card/mmc_test.c   |  340 +++++++++++++++++++++++++++-
drivers/mmc/card/queue.c      |  180 ++++++++++------
drivers/mmc/card/queue.h      |   31 ++-
drivers/mmc/core/core.c       |  132 ++++++++++-
drivers/mmc/core/debugfs.c    |    5 +
drivers/mmc/host/mmci.c       |  146 +++++++++++-
drivers/mmc/host/mmci.h       |    8 +
drivers/mmc/host/omap_hsmmc.c |   90 +++++++-
include/linux/mmc/core.h      |    9 +-
include/linux/mmc/host.h      |   13 +-
lib/Kconfig.debug             |   11 +
12 files changed, 1174 insertions(+), 284 deletions(-)

--
1.7.4.1

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