The following is the latest attempt at a rewriting the MMC/SD stack to cope with multiqueueing. If you just want to grab a branch and test the patches with your hardware, I put a git branch with this series here: https://git.kernel.org/cgit/linux/kernel/git/linusw/linux-stericsson.git/log/?h=mmc-mq-next-2017-02-09 It's based on Ulf's v4.10-rc3-based tree, so quick reminder: git checkout -b test v4.10-rc3 git pull git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-stericsson.git mmc-mq-next-2017-02-09 Should get you a testable "test" branch. These patches are clearly v4.12 material. They get increasinly controversial and needing review the further into the series you go. The last patch for multiqueue is marked RFC for a reason. Every time I do this it seems to be an extensive rewrite of the whole world. Anyways this is based on the other ~16 patches that were already merged for the upcoming v4.11. The rationale for this approach was Arnd's suggestion to try to switch the MMC/SD stack around so as to complete requests as quickly as possible from the device driver so that new requests can be issued. We are doing this now: the polling loop that was pulling NULL out of the request queue and driving the pipeline with a loop is gone. We are not issueing new requests from interrupt context: I still have to post a work for it. I don't know if that is possible. There is the retune and background operations that need to be checked after every command and yeah, it needs to happen in blocking context as far as I know. We have parallelism in pre/post hooks also with multiqueue. All asynchronous optimization that was there for the old block layer is now also there for multiqueue. There is even a new interesting optimization that make bounce buffers be bounced asynchronously with this change. We still use the trick to set the queue depth to 2 to get two parallel requests pushed down to the host. Adrian: I know I made quite extensive violence on your queueue handling reusing it in a way that is probably totally counter to your command queueing patch series. I'm sorry. I guess you can see where it is going if you follow the series. I also killed the host context, right off, after reducing the synchronization needs to zero. I hope you will be interested in the result though! Does this perform? The numbers follow. I will discuss my conclusions after the figures. All the tests are done on a cold booted Ux500 system. Before this patch series, based on my earlier cleanups and refactorings on Ulf's next branch ending with "mmc: core: start to break apart mmc_start_areq()": time dd if=/dev/mmcblk0 of=/dev/null bs=1M count=1024 1024+0 records in 1024+0 records out 1073741824 bytes (1.0GB) copied, 45.126404 seconds, 22.7MB/s real 0m 45.13s user 0m 0.02s sys 0m 7.60s mount /dev/mmcblk0p1 /mnt/ cd /mnt/ time find . > /dev/null real 0m 3.61s user 0m 0.30s sys 0m 1.56s Command line used: iozone -az -i0 -i1 -i2 -s 20m -I -f /mnt/foo.test Output is in kBytes/sec random random kB reclen write rewrite read reread read write 20480 4 2046 2114 5981 6008 5971 40 20480 8 4825 4622 9104 9118 9070 81 20480 16 5767 5929 12250 12253 12209 166 20480 32 6242 6303 14920 14917 14879 337 20480 64 6598 5907 16758 16760 16739 695 20480 128 6807 6837 17863 17869 17788 1387 20480 256 6922 6925 18497 18490 18482 3076 20480 512 7273 7313 18636 18407 18829 7344 20480 1024 7339 7332 17695 18785 18472 7441 20480 2048 7419 7471 19166 18812 18797 7474 20480 4096 7598 7714 21006 20975 21180 7708 20480 8192 7632 7830 22328 22315 22201 7828 20480 16384 7412 7903 23070 23046 22849 7913 With "mmc: core: move the asynchronous post-processing" time dd if=/dev/mmcblk0 of=/dev/null bs=1M count=1024 1024+0 records in 1024+0 records out 1073741824 bytes (1.0GB) copied, 52.166992 seconds, 19.6MB/s real 0m 52.17s user 0m 0.01s sys 0m 6.96s mount /dev/mmcblk0p1 /mnt/ cd /mnt/ time find . > /dev/null real 0m 3.88s user 0m 0.35s sys 0m 1.60s Command line used: iozone -az -i0 -i1 -i2 -s 20m -I -f /mnt/foo.test Output is in kBytes/sec random random kB reclen write rewrite read reread read write 20480 4 2072 2200 6030 6066 6005 40 20480 8 4847 5106 9174 9178 9123 81 20480 16 5791 5934 12301 12299 12260 166 20480 32 6252 6311 14906 14943 14919 337 20480 64 6607 6699 16776 16787 16756 690 20480 128 6836 6880 17868 17880 17873 1419 20480 256 6967 6955 18442 17112 18490 3072 20480 512 7320 7359 18818 18738 18477 7310 20480 1024 7350 7426 18297 18551 18357 7429 20480 2048 7439 7476 18035 19111 17670 7486 20480 4096 7655 7728 19688 19557 19758 7738 20480 8192 7640 7848 20675 20718 20787 7823 20480 16384 7489 7934 21225 21186 21555 7943 With "mmc: queue: issue requests in massive parallel" time dd if=/dev/mmcblk0 of=/dev/null bs=1M count=1024 1024+0 records in 1024+0 records out 1073741824 bytes (1.0GB) copied, 49.308167 seconds, 20.8MB/s real 0m 49.31s user 0m 0.00s sys 0m 7.11s mount /dev/mmcblk0p1 /mnt/ cd /mnt/ time find . > /dev/null real 0m 3.70s user 0m 0.19s sys 0m 1.73s Command line used: iozone -az -i0 -i1 -i2 -s 20m -I -f /mnt/foo.test Output is in kBytes/sec random random kB reclen write rewrite read reread read write 20480 4 1709 1761 5963 5321 5909 40 20480 8 4736 5059 9089 9092 9055 81 20480 16 5772 5928 12217 12229 12184 165 20480 32 6237 6279 14898 14899 14875 336 20480 64 6599 6663 16759 16760 16741 683 20480 128 6804 6790 17869 17869 17864 1393 20480 256 6863 6883 18485 18488 18501 3105 20480 512 7223 7249 18807 18810 18812 7259 20480 1024 7311 7321 18684 18467 18201 7328 20480 2048 7405 7457 18560 18044 18343 7451 20480 4096 7596 7684 20742 21154 21153 7711 20480 8192 7593 7802 21743 21721 22090 7804 20480 16384 7399 7873 21539 22670 22828 7876 With "RFC: mmc: switch MMC/SD to use blk-mq multiqueueing v3" time dd if=/dev/mmcblk0 of=/dev/null bs=1M count=1024 1024+0 records in 1024+0 records out 1073741824 bytes (1.0GB) copied, 46.240479 seconds, 22.1MB/s real 0m 46.25s user 0m 0.03s sys 0m 6.42s mount /dev/mmcblk0p1 /mnt/ cd /mnt/ time find . > /dev/null real 0m 4.13s user 0m 0.40s sys 0m 1.64s Command line used: iozone -az -i0 -i1 -i2 -s 20m -I -f /mnt/foo.test Output is in kBytes/sec random random kB reclen write rewrite read reread read write 20480 4 1786 1806 6055 6061 5360 40 20480 8 4849 5088 9167 9175 9120 81 20480 16 5807 5975 12273 12256 12240 166 20480 32 6275 6317 14929 14931 14905 338 20480 64 6629 6708 16755 16783 16758 688 20480 128 6856 6884 17890 17804 17873 1420 20480 256 6927 6946 18104 17826 18389 3038 20480 512 7296 7280 18720 18752 18819 7284 20480 1024 7286 7415 18583 18598 18516 7403 20480 2048 7435 7470 18378 18268 18682 7471 20480 4096 7670 7786 21364 21275 20761 7766 20480 8192 7637 7868 22193 21994 22100 7850 20480 16384 7416 7921 23050 23051 22726 7955 The iozone results seem a bit consistent and all values seem to be noisy and not say much. I don't know why really, maybe the test is simply not relevant, the tests don't seem to be significantly affected by any of the patches, so let's focus on the dd and find tests. You can see there are three steps: - I do some necessary refactoring and need to move postprocessing to after the requests have been completed. This clearly, as you can see, introduce a performance regression in the dd test with the patch: "mmc: core: move the asynchronous post-processing" It seems the random seek with find isn't much affected. - I continue the refactoring and get to the point of issueing requests immediately after every successful transfer, and the dd performance is restored with patch "mmc: queue: issue requests in massive parallel" - Then I add multiqueue on top of the cake. So before the change we have the nice performance we want so we can study the effect of just introducing multiqueueing in the last patch "RFC: mmc: switch MMC/SD to use blk-mq multiqueueing v3" What immediately jumps out at you is that linear read/writes perform just as nicely or actually better with MQ than with the old block layer. What is amazing is that just a little randomness, such as the find . > /dev/null immediately seems to visibly regress with MQ. My best guess is that it is caused by the absence of the block scheduler. I do not know if my conclusions are right or anything, please scrutinize. Linus Walleij (16): mmc: core: move some code in mmc_start_areq() mmc: core: refactor asynchronous request finalization mmc: core: refactor mmc_request_done() mmc: core: move the asynchronous post-processing mmc: core: add a kthread for completing requests mmc: core: replace waitqueue with worker mmc: core: do away with is_done_rcv mmc: core: do away with is_new_req mmc: core: kill off the context info mmc: queue: simplify queue logic mmc: block: shuffle retry and error handling mmc: queue: stop flushing the pipeline with NULL mmc: queue: issue struct mmc_queue_req items mmc: queue: get/put struct mmc_queue_req mmc: queue: issue requests in massive parallel RFC: mmc: switch MMC/SD to use blk-mq multiqueueing v3 drivers/mmc/core/block.c | 426 +++++++++++++++++++++++------------------------ drivers/mmc/core/block.h | 10 +- drivers/mmc/core/bus.c | 1 - drivers/mmc/core/core.c | 228 ++++++++++++------------- drivers/mmc/core/core.h | 2 - drivers/mmc/core/host.c | 2 +- drivers/mmc/core/queue.c | 337 ++++++++++++++----------------------- drivers/mmc/core/queue.h | 21 ++- include/linux/mmc/core.h | 9 +- include/linux/mmc/host.h | 24 +-- 10 files changed, 481 insertions(+), 579 deletions(-) -- 2.9.3 -- 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
