Hi Per.. it is interesting approach..so we want to test your double buffering in our environment(Samsung SoC). Did you test with SDHCI? If you tested with SDHCI, i want to know how much increase the performance. Thanks, Jaehoon Chung Per Forlin wrote: > Add support to prepare one MMC request while another is active on > the host. This is done by making the issue_rw_rq() asynchronous. > The increase in throughput is proportional to the time it takes to > prepare 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 U8500 on eMMC shows significant performance gain for DMA on MMC for large > reads. In the PIO case there is some gain in performance for large reads too. > There seems to be no or small performance gain for write, don't have a good > explanation for this yet. > > There are two optional hooks pre_req() and post_req() that the host driver > may implement in order to improve double buffering. In the DMA case pre_req() > may do dma_map_sg() and prepare the dma descriptor and post_req runs the > dma_unmap_sg. > > The mmci host driver implementation for double buffering is not intended > nor ready for mainline yet. It is only an example of how to implement > pre_req() and post_req(). The reason for this is that the basic DMA support > for MMCI is not complete yet. The mmci patches are sent in a separate patch > series "[FYI 0/4] arm: mmci: example implementation of double buffering". > > Issues/Questions for issue_rw_rq() in block.c: > * Is it safe to claim the host for the first MMC request and wait to release > it until the MMC queue is empty again? Or must the host be claimed and > released for every request? > * Is it possible to predict the result from __blk_end_request(). > If there are no errors for a completed MMC request and the > blk_rq_bytes(req) == data.bytes_xfered, will it be guaranteed that > __blk_end_request will return 0? > > Here follows the IOZone results for u8500 v1.1 on eMMC. > The numbers for DMA are a bit to good here due to the fact that the > CPU speed is decreased compared to u8500 v2. This makes the cache handling > even more significant. > > Command line used: ./iozone -az -i0 -i1 -i2 -s 50m -I -f /iozone.tmp -e -R -+u > > Relative diff: VANILLA-MMC-PIO -> 2BUF-MMC-PIO > cpu load is abs diff > random random > KB reclen write rewrite read reread read write > 51200 4 +0% +0% +0% +0% +0% +0% > cpu: +0.1 -0.1 -0.5 -0.3 -0.1 -0.0 > > 51200 8 +0% +0% +6% +6% +8% +0% > cpu: +0.1 -0.1 -0.3 -0.4 -0.8 +0.0 > > 51200 16 +0% -2% +0% +0% -3% +0% > cpu: +0.0 -0.2 +0.0 +0.0 -0.2 +0.0 > > 51200 32 +0% +1% +0% +0% +0% +0% > cpu: +0.1 +0.0 -0.3 +0.0 +0.0 +0.0 > > 51200 64 +0% +0% +0% +0% +0% +0% > cpu: +0.1 +0.0 +0.0 +0.0 +0.0 +0.0 > > 51200 128 +0% +1% +1% +1% +1% +0% > cpu: +0.0 +0.2 +0.1 -0.3 +0.4 +0.0 > > 51200 256 +0% +0% +1% +1% +1% +0% > cpu: +0.0 -0.0 +0.1 +0.1 +0.1 +0.0 > > 51200 512 +0% +1% +2% +2% +2% +0% > cpu: +0.1 +0.0 +0.2 +0.2 +0.2 +0.1 > > 51200 1024 +0% +2% +2% +2% +3% +0% > cpu: +0.2 +0.1 +0.2 +0.5 -0.8 +0.0 > > 51200 2048 +0% +2% +3% +3% +3% +0% > cpu: +0.0 -0.2 +0.4 +0.8 -0.5 +0.2 > > 51200 4096 +0% +1% +3% +3% +3% +1% > cpu: +0.2 +0.1 +0.9 +0.9 +0.5 +0.1 > > 51200 8192 +1% +0% +3% +3% +3% +1% > cpu: +0.2 +0.2 +1.3 +1.3 +1.0 +0.0 > > 51200 16384 +0% +1% +3% +3% +3% +1% > cpu: +0.2 +0.1 +1.0 +1.3 +1.0 +0.5 > > Relative diff: VANILLA-MMC-DMA -> 2BUF-MMC-MMCI-DMA > cpu load is abs diff > random random > KB reclen write rewrite read reread read write > 51200 4 +0% -3% +6% +5% +5% +0% > cpu: +0.0 -0.2 -0.6 -0.1 +0.3 +0.0 > > 51200 8 +0% +0% +7% +7% +7% +0% > cpu: +0.0 +0.1 +0.8 +0.6 +0.9 +0.0 > > 51200 16 +0% +0% +7% +7% +8% +0% > cpu: +0.0 -0.0 +0.7 +0.7 +0.8 +0.0 > > 51200 32 +0% +0% +8% +8% +9% +0% > cpu: +0.0 +0.1 +0.7 +0.7 +0.3 +0.0 > > 51200 64 +0% +1% +9% +9% +9% +0% > cpu: +0.0 +0.0 +0.8 +0.7 +0.8 +0.0 > > 51200 128 +1% +0% +13% +13% +14% +0% > cpu: +0.2 +0.0 +1.0 +1.0 +1.1 +0.0 > > 51200 256 +1% +2% +8% +8% +11% +0% > cpu: +0.0 +0.3 +0.0 +0.7 +1.5 +0.0 > > 51200 512 +1% +2% +16% +16% +17% +0% > cpu: +0.2 +0.2 +2.2 +2.1 +2.2 +0.1 > > 51200 1024 +1% +2% +20% +20% +20% +1% > cpu: +0.2 +0.1 +2.6 +1.9 +2.6 +0.0 > > 51200 2048 +0% +2% +22% +22% +21% +0% > cpu: +0.0 +0.3 +2.3 +2.9 +2.1 -0.0 > > 51200 4096 +1% +2% +23% +23% +23% +1% > cpu: +0.2 +0.1 +2.0 +3.2 +3.1 +0.0 > > 51200 8192 +1% +5% +24% +24% +24% +1% > cpu: +1.4 -0.0 +4.2 +3.0 +2.8 +0.1 > > 51200 16384 +1% +3% +24% +24% +24% +2% > cpu: +0.0 +0.3 +3.4 +3.8 +3.7 +0.1 > > Here follows the IOZone results for u5500 on eMMC. > These numbers for DMA are more as expected. > > Command line used: ./iozone -az -i0 -i1 -i2 -s 50m -I -f /iozone.tmp -e -R -+u > > Relative diff: VANILLA-MMC-DMA -> 2BUF-MMC-MMCI-DMA > cpu load is abs diff > random random > KB reclen write rewrite read reread read write > 51200 128 +1% +1% +10% +9% +10% +0% > cpu: +0.1 +0.0 +1.3 +0.1 +0.8 +0.1 > > 51200 256 +2% +2% +7% +7% +9% +0% > cpu: +0.1 +0.4 +0.5 +0.6 +0.7 +0.0 > > 51200 512 +2% +2% +12% +12% +12% +1% > cpu: +0.4 +0.6 +1.8 +2.4 +2.4 +0.2 > > 51200 1024 +2% +3% +14% +14% +14% +0% > cpu: +0.3 +0.1 +2.1 +1.4 +1.4 +0.2 > > 51200 2048 +3% +3% +16% +16% +16% +1% > cpu: +0.2 +0.2 +2.5 +1.8 +2.4 -0.2 > > 51200 4096 +3% +3% +17% +17% +18% +3% > cpu: +0.1 -0.1 +2.7 +2.0 +2.7 -0.1 > > 51200 8192 +3% +3% +18% +18% +18% +3% > cpu: -0.1 +0.2 +3.0 +2.3 +2.2 +0.2 > > 51200 16384 +3% +3% +18% +18% +18% +4% > cpu: +0.2 +0.2 +2.8 +3.5 +2.4 -0.0 > > Per Forlin (5): > mmc: add member in mmc queue struct to hold request data > mmc: Add a block request prepare function > mmc: Add a second mmc queue request member > mmc: Store the mmc block request struct in mmc queue > mmc: Add double buffering for mmc block requests > > drivers/mmc/card/block.c | 337 ++++++++++++++++++++++++++++++---------------- > drivers/mmc/card/queue.c | 171 +++++++++++++++--------- > drivers/mmc/card/queue.h | 31 +++- > drivers/mmc/core/core.c | 77 +++++++++-- > include/linux/mmc/core.h | 7 +- > include/linux/mmc/host.h | 8 + > 6 files changed, 432 insertions(+), 199 deletions(-) > > -- > 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 > -- 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
