On Thu, Jun 30, 2011 at 6:06 PM, Poddar, Sourav <sourav.poddar@xxxxxx> wrote: > On Tue, Jun 28, 2011 at 1:41 PM, 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 non-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 non-blocking mmc request makes it >> possible to prepare the caches for next job in parallel to an active >> mmc request. >> >> This is done by making the issue_rw_rq() non-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 v7: >> * rebase on mmc-next, on top of Russell's updated error handling. >> * Clarify description of mmc_start_req() >> * Resolve compile without CONFIG_DMA_ENIGNE issue for mmci >> * Add mmc test to measure how performance is affected by sg length >> * Add missing wait_for_busy in mmc_test non-blocking test. This call got lost >> in v4 of this patchset when refactoring mmc_start_req. >> * Add sub-prefix (core block queue) to relevant patches. >> >> Per Forlin (12): >> mmc: core: add non-blocking mmc request function >> 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 non-blocking transfers >> mmc: mmc_test: test to measure how sg_len affect performance >> mmc: block: add member in mmc queue struct to hold request data >> mmc: block: add a block request prepare function >> mmc: block: move error code in issue_rw_rq to a separate function. >> mmc: queue: add a second mmc queue request member >> mmc: core: add random fault injection >> mmc: block: add handling for two parallel block requests in >> issue_rw_rq >> >> drivers/mmc/card/block.c | 505 ++++++++++++++++++++++++----------------- >> drivers/mmc/card/mmc_test.c | 491 ++++++++++++++++++++++++++++++++++++++-- >> drivers/mmc/card/queue.c | 184 ++++++++++------ >> drivers/mmc/card/queue.h | 33 ++- >> drivers/mmc/core/core.c | 167 +++++++++++++- >> drivers/mmc/core/debugfs.c | 5 + >> drivers/mmc/host/mmci.c | 147 +++++++++++- >> drivers/mmc/host/mmci.h | 8 + >> drivers/mmc/host/omap_hsmmc.c | 87 +++++++- >> include/linux/mmc/core.h | 6 +- >> include/linux/mmc/host.h | 24 ++ >> lib/Kconfig.debug | 11 + >> 12 files changed, 1345 insertions(+), 323 deletions(-) > > > > Boot tested on Omap4430 Blaze board. > > Tested-by: Sourav Poddar<sourav.poddar@xxxxxx> > Reviewed for OMAP along with Sourav's tests.. Reviewed-by: Venkatraman S <svenkatr@xxxxxx> -- 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
