1 MiB erase blocks, possibly. 7 open-au linear. 5 open-au random. dd speed at the end is puzzling given the flashbench speeds.
andrew@lati:~/git/flashbench$ sudo fdisk -l /dev/mmcblk0 | grep Disk Disk /dev/mmcblk0: 7888 MB, 7888437248 bytes Disk identifier: 0x00000000
andrew@lati:~/git/flashbench$ factor 7888437248 7888437248: 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 7523
andrew@lati:~/git/flashbench$ head /sys/block/mmcblk0/device/* 2>/dev/null | grep -v ^$ ==> /sys/block/mmcblk0/device/block <== ==> /sys/block/mmcblk0/device/cid <== 1b534d3030303030100dd6253900da00 ==> /sys/block/mmcblk0/device/csd <== 400e00325b5900003ac57f800a400000 ==> /sys/block/mmcblk0/device/date <== 10/2013 ==> /sys/block/mmcblk0/device/driver <== ==> /sys/block/mmcblk0/device/erase_size <== 512 ==> /sys/block/mmcblk0/device/fwrev <== 0x0 ==> /sys/block/mmcblk0/device/hwrev <== 0x1 ==> /sys/block/mmcblk0/device/manfid <== 0x00001b ==> /sys/block/mmcblk0/device/name <== 00000 ==> /sys/block/mmcblk0/device/oemid <== 0x534d ==> /sys/block/mmcblk0/device/power <== ==> /sys/block/mmcblk0/device/preferred_erase_size <== 4194304 ==> /sys/block/mmcblk0/device/scr <== 0235800300000000 ==> /sys/block/mmcblk0/device/serial <== 0x0dd62539 ==> /sys/block/mmcblk0/device/subsystem <== ==> /sys/block/mmcblk0/device/type <== SD ==> /sys/block/mmcblk0/device/uevent <== DRIVER=mmcblk MMC_TYPE=SD MMC_NAME=00000 MODALIAS=mmc:block
andrew@lati:~/git/flashbench$ sudo ./flashbench /dev/mmcblk0 -a --blocksize=1024 --count=100 align 2147483648 pre 500µs on 726µs post 558µs diff 197µs align 1073741824 pre 513µs on 725µs post 546µs diff 196µs align 536870912 pre 507µs on 727µs post 554µs diff 196µs align 268435456 pre 510µs on 723µs post 549µs diff 194µs align 134217728 pre 502µs on 704µs post 545µs diff 180µs align 67108864 pre 509µs on 708µs post 548µs diff 180µs align 33554432 pre 498µs on 710µs post 550µs diff 186µs align 16777216 pre 499µs on 710µs post 551µs diff 185µs align 8388608 pre 502µs on 706µs post 567µs diff 172µs align 4194304 pre 499µs on 708µs post 539µs diff 188µs align 2097152 pre 500µs on 728µs post 568µs diff 194µs align 1048576 pre 513µs on 750µs post 601µs diff 193µs align 524288 pre 514µs on 743µs post 596µs diff 188µs align 262144 pre 519µs on 732µs post 574µs diff 186µs align 131072 pre 510µs on 764µs post 608µs diff 206µs align 65536 pre 510µs on 755µs post 602µs diff 199µs align 32768 pre 515µs on 742µs post 591µs diff 188µs align 16384 pre 507µs on 723µs post 570µs diff 185µs align 8192 pre 503µs on 717µs post 564µs diff 183µs align 4096 pre 576µs on 582µs post 569µs diff 9.44µs align 2048 pre 582µs on 584µs post 568µs diff 9.08µs
andrew@lati:~/git/flashbench$ sudo ./flashbench /dev/mmcblk0 --open-au --blocksize=$[16*1024] --erasesize=$[1*1024*1024] --open-au-nr=1 1MiB 13.2M/s 512KiB 13.1M/s 256KiB 13M/s 128KiB 13M/s 64KiB 12.9M/s 32KiB 10.5M/s 16KiB 7.84M/s
andrew@lati:~/git/flashbench$ sudo ./flashbench /dev/mmcblk0 --open-au --blocksize=$[16*1024] --erasesize=$[1*1024*1024] --open-au-nr=7 1MiB 6.69M/s 512KiB 13.1M/s 256KiB 12.6M/s 128KiB 12M/s 64KiB 11M/s 32KiB 8.13M/s 16KiB 5.43M/s
andrew@lati:~/git/flashbench$ sudo ./flashbench /dev/mmcblk0 --open-au --blocksize=$[16*1024] --erasesize=$[1*1024*1024] --open-au-nr=8 1MiB 2.22M/s 512KiB 2.29M/s 256KiB 2.21M/s ^C
andrew@lati:~/git/flashbench$ sudo ./flashbench /dev/mmcblk0 --open-au --blocksize=$[16*1024] --erasesize=$[1*1024*1024] --random --open-au-nr=5 1MiB 12.7M/s 512KiB 12.8M/s 256KiB 13.1M/s 128KiB 12.3M/s 64KiB 11.8M/s 32KiB 8.27M/s 16KiB 5.7M/s
andrew@lati:~/git/flashbench$ sudo ./flashbench /dev/mmcblk0 --open-au --blocksize=$[16*1024] --erasesize=$[1*1024*1024] --random --open-au-nr=6 1MiB 4.14M/s 512KiB 4.17M/s 256KiB 6.28M/s 128KiB 4.11M/s 64KiB 2.98M/s 32KiB 2.74M/s 16KiB 1.97M/s
andrew@lati:~/git/flashbench$ sudo dd if=/dev/zero of=/dev/mmcblk0 bs=1M count=100 oflag=direct 100+0 records in 100+0 records out 104857600 bytes (105 MB) copied, 20.3286 s, 5.2 MB/s