On 16 June 2011 15:39, S, Venkatraman <svenkatr@xxxxxx> wrote: > On Thu, May 26, 2011 at 3:27 AM, Per Forlin <per.forlin@xxxxxxxxxx> 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 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 >> >> Changes since v3: >> * Based on 2.6.39-rc7 >> * Add error check for testlist in mmc_test.c >> * Resolve in mmc-queue-thread that caused the mmc-thread to miss a wakeup. >> * Move parallel request handling to core.c. This simplifies the interface >> from 4 public functions to 1. This also gives access for SDIO to use the >> same functionallity, even though the function is not tuned for the SDIO >> execution flow yet. >> >> Per Forlin (12): >> mmc: add none blocking mmc request function >> 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() >> 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: test: add random fault injection in core.c >> mmc: add handling for two parallel block requests in issue_rw_rq >> >> drivers/mmc/card/block.c | 452 +++++++++++++++++++++++++---------------- >> drivers/mmc/card/mmc_test.c | 361 ++++++++++++++++++++++++++++++++- >> drivers/mmc/card/queue.c | 184 +++++++++++------ >> drivers/mmc/card/queue.h | 32 +++- >> drivers/mmc/core/core.c | 165 ++++++++++++++- >> 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 | 6 +- >> include/linux/mmc/host.h | 19 ++ >> lib/Kconfig.debug | 11 + >> 12 files changed, 1187 insertions(+), 292 deletions(-) >> > > Nitpick.. The mmc_test.c changes should be at the end of the series, > after the async feature is available. > mmc_test sits on top of core.c It doesn't test any code in the mmc block device. I use DT (data test) together with random fault generation to verify the mmc block device code. >> mmc: add none blocking mmc request function >> 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() >> mmc: mmc_test: add debugfs file to list all tests >> mmc: mmc_test: add test for none blocking transfers These patches are enough to run mmc_tests for async request for omap_hsmmc and mmci. Regards, Per -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
