On Wed, Jan 17 2018 at 2:33pm -0500, Heinz Mauelshagen <heinzm@xxxxxxxxxx> wrote: > 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 My initial thought for dm-ram was: why? (considering we have brd and pmem and null_blk). But for 100 lines of code if nothing else it could serve as yet another example DM target for those interested in learning more about how to implement a DM target. Would be good to compare its performance with brd, null_blk and pmem though. As for dm-loop, doubling the performance of the loopback driver is quite nice (especially with only 1/7 the number of lines of code as drives/block/loop.c). I'll review both of these closer in the coming days but it is getting _really_ close to the 4.16 merge window (likley opens Sunday) So they may have to wait until 4.17. We'll see. Thanks, Mike -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
