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Date: Thu, 12 May 2011 13:28:09 +0900 From: Jaehoon Chung <jh80.chung@...sung.com> To: Philip Rakity <prakity@...vell.com> Cc: Per Forlin <per.forlin@...aro.org>, "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linaro-dev@...ts.linaro.org" <linaro-dev@...ts.linaro.org>, Chris Ball <cjb@...top.org> Subject: Re: [PATCH v3 00/12] mmc: use nonblock mmc requests to minimize latency 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: > >> On 9 May 2011 04:05, Philip Rakity <prakity@...vell.com> wrote: >>> 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 > >>> I believe ADMA will do large transfers. Another data point. >>> >>> Philip >> Thanks, >> Per >> >>> On May 7, 2011, at 12:14 PM, Per Forlin wrote: >>> >>>> 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 >>>> >>>> -- >>>> To unsubscribe from this list: send the line "unsubscribe linux-mmc" in >>>> the body of a message to majordomo@...r.kernel.org >>>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>> > > -- > To unsubscribe from this list: send the line "unsubscribe linux-mmc" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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