Enhancing IO performance compared to the kernels existing loop driver thus better suiting respective requirements in test setups, this patch series adds new "loop" and "ram" targets. For measures see test results below. The "loop" target maps segments to backing files. Mapping table example: 0 4192256 loop /tmp/mapper_loop1 4192256 2097152 loop /dev/nvm/mapper_loop0 The "ram" target accesses RAM directly rather than through tmpfs additionally enhancing performance compared to "loop" thus avoding filesystem overhead. Mapping table example: 0 8388608 ram "ram" is a singleton target. Performance test results for 4K and 32K IOPS comparing the loop driver with dm-loop backed by tmpfs and dm-ram (all 2GiB backing size): <TESTSCRIPT> #!/bin/sh for f in /tmp/loop0 /tmp/mapper_loop0 do dd if=/dev/zero of=$f bs=256M count=8 iflag=fullblock done losetup /dev/loop0 /tmp/loop0 sectors=`du -s /tmp/mapper_loop0|cut -f1` dmsetup create loop0 --table "0 $sectors loop /tmp/mapper_loop0" dmsetup create ram --table "0 $sectors ram" for bs in 4K 32K do for d in /dev/loop0 /dev/mapper/loop0 /dev/mapper/ram do echo 3 > /proc/sys/vm/drop_caches fio --bs=$bs --rw=randrw --numjobs=99 --group_reporting --iodepth=12 --runtime=3 --ioengine=libaio \ --loops=1 --direct=1 --exitall --name dc --filename=$d | egrep "read|write" done done </TESTSCRIPT> <4K_RESULTS> loop driver: read: IOPS=226k, BW=881MiB/s (924MB/s)(2645MiB/3003msec) write: IOPS=225k, BW=880MiB/s (923MB/s)(2643MiB/3003msec) dm-loop target: read: IOPS=425k, BW=1661MiB/s (1742MB/s)(4990MiB/3004msec) write: IOPS=425k, BW=1662MiB/s (1743MB/s)(4992MiB/3004msec) dm-ram target: read: IOPS=636k, BW=2484MiB/s (2605MB/s)(7464MiB/3005msec) write: IOPS=636k, BW=2484MiB/s (2605MB/s)(7464MiB/3005msec) </4K_RESULTS> <32K_RESULTS> loop driver: read: IOPS=55.5k, BW=1733MiB/s (1817MB/s)(5215MiB/3009msec) write: IOPS=55.2k, BW=1726MiB/s (1810MB/s)(5195MiB/3009msec) dm-loop target: read: IOPS=110k, BW=3452MiB/s (3620MB/s)(10.1GiB/3006msec) write: IOPS=110k, BW=3448MiB/s (3615MB/s)(10.1GiB/3006msec) dm-ram target: read: IOPS=355k, BW=10.8GiB/s (11.6GB/s)(32.6GiB/3008msec) write: IOPS=355k, BW=10.8GiB/s (11.6GB/s)(32.6GiB/3008msec) </32K_RESULTS> Signed-off-by: Heinz Mauelshagen <heinzm@xxxxxxxxxx> Heinz Mauelshagen (2): dm loop: new target redirecting io to backing file(s) dm ram: new target redirecting io to RAM Documentation/device-mapper/loop.txt | 20 ++ Documentation/device-mapper/ram.txt | 15 ++ drivers/md/Kconfig | 14 ++ drivers/md/Makefile | 2 + drivers/md/dm-loop.c | 352 +++++++++++++++++++++++++++++++++++ drivers/md/dm-ram.c | 101 ++++++++++ 6 files changed, 504 insertions(+) create mode 100644 Documentation/device-mapper/loop.txt create mode 100644 Documentation/device-mapper/ram.txt create mode 100644 drivers/md/dm-loop.c create mode 100644 drivers/md/dm-ram.c -- 2.14.3 -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
