u@u:~/flash/flashbench$ sudo ./flashbench -a /dev/mmcblk0  --blocksize=1024
align 536870912	pre 1.49ms	on 3.42ms	post 3.06ms	diff 1.15ms
align 268435456	pre 1.51ms	on 3.7ms	post 3.09ms	diff 1.4ms
align 134217728	pre 2.19ms	on 3.64ms	post 3.05ms	diff 1.03ms
align 67108864	pre 1.49ms	on 3.53ms	post 3.1ms	diff 1.23ms
align 33554432	pre 2.45ms	on 3.79ms	post 3.12ms	diff 999µs
align 16777216	pre 1.46ms	on 3.52ms	post 3.1ms	diff 1.24ms
align 8388608	pre 1.46ms	on 3.52ms	post 3.1ms	diff 1.24ms
align 4194304	pre 1.46ms	on 3.52ms	post 3.1ms	diff 1.24ms
align 2097152	pre 1.46ms	on 3.52ms	post 3.1ms	diff 1.24ms
align 1048576	pre 2.02ms	on 3.79ms	post 3.12ms	diff 1.22ms
align 524288	pre 2.22ms	on 2.39ms	post 2.41ms	diff 77.6µs
align 262144	pre 2.43ms	on 2.61ms	post 2.61ms	diff 95.8µs
align 131072	pre 2.58ms	on 2.77ms	post 2.73ms	diff 111µs
align 65536	pre 2.65ms	on 2.87ms	post 2.74ms	diff 169µs
align 32768	pre 2.7ms	on 2.88ms	post 2.84ms	diff 107µs
align 16384	pre 2.73ms	on 2.91ms	post 2.87ms	diff 111µs
align 8192	pre 2.74ms	on 2.92ms	post 2.88ms	diff 109µs
align 4096	pre 2.9ms	on 2.86ms	post 2.83ms	diff -7395ns
align 2048	pre 2.88ms	on 2.87ms	post 2.86ms	diff 2.28µs
u@u:~/flash/flashbench$

u@u:~/flash/flashbench$ sudo ./flashbench -O --erasesize=$[4 * 1024 * 1024] --blocksize=$[256 * 1024] /dev/mmcblk0  --open-au-nr=2
4MiB    6.36M/s 
2MiB    6.24M/s 
1MiB    6.17M/s 
512KiB  6.19M/s 
256KiB  6.22M/s 
u@u:~/flash/flashbench$

u@u:~/flash/flashbench$ sudo ./flashbench -O --erasesize=$[4 * 1024 * 1024] --blocksize=$[256 * 1024] /dev/mmcblk0  --open-au-nr=3
4MiB    6.25M/s 
2MiB    6.25M/s 
1MiB    6.24M/s 
512KiB  2.53M/s 
256KiB  1.14M/s 
u@u:~/flash/flashbench$