FlashBench
Benchmarking flash media to determine allocation units and page sizes
Flashbench Source
github : https://github.com/bradfa/flashbench
Samsung Evo 32GB
Make : Samsung
Class : Class 10, UHS-1
Capacity : 32GB
Allocation Unit : 16MB
Write Size : ??
Page Size : ??
Bench
sudo ./flashbench -a /dev/sdj --count=100 --blocksize=1024
align 8589934592 pre 1.55ms on 1.85ms post 1.46ms diff 343µs
align 4294967296 pre 1.56ms on 1.85ms post 1.48ms diff 330µs
align 2147483648 pre 1.55ms on 1.87ms post 1.55ms diff 321µs
align 1073741824 pre 1.53ms on 1.75ms post 1.39ms diff 288µs
align 536870912 pre 1.51ms on 1.75ms post 1.39ms diff 297µs
align 268435456 pre 1.57ms on 1.77ms post 1.37ms diff 296µs
align 134217728 pre 1.53ms on 1.85ms post 1.48ms diff 348µs
align 67108864 pre 1.53ms on 1.87ms post 1.55ms diff 328µs
align 33554432 pre 1.53ms on 1.85ms post 1.48ms diff 348µs
align 16777216 pre 1.53ms on 1.75ms post 1.37ms diff 297µs **
align 8388608 pre 1.43ms on 1.6ms post 1.39ms diff 188µs
align 4194304 pre 1.42ms on 1.59ms post 1.39ms diff 188µs
align 2097152 pre 1.42ms on 1.6ms post 1.37ms diff 205µs
align 1048576 pre 1.47ms on 1.6ms post 1.37ms diff 178µs
align 524288 pre 1.39ms on 1.6ms post 1.37ms diff 220µs
align 262144 pre 1.43ms on 1.6ms post 1.37ms diff 208µs
align 131072 pre 1.43ms on 1.6ms post 1.37ms diff 204µs
align 65536 pre 1.37ms on 1.6ms post 1.39ms diff 223µs
align 32768 pre 1.37ms on 1.6ms post 1.37ms diff 232µs
align 16384 pre 1.37ms on 1.6ms post 1.37ms diff 233µs **
align 8192 pre 1.37ms on 1.37ms post 1.37ms diff -1225ns
align 4096 pre 1.37ms on 1.37ms post 1.37ms diff 932ns
align 2048 pre 1.37ms on 1.37ms post 1.37ms diff 2.79µs
Analysis
- 16MB boundary has performance penalty = allocation unit
- 16KB performance penalty = page size
Sandisk Ultra
Make : Sandisk
Class : Class 10, UHS-1
Capacity : 16GB
Allocation Unit : ??
Write Size : ??
Page Size : ??
Bench
sudo ./flashbench -a /dev/sdi --count=100 --blocksize=1024
align 4294967296 pre 1.24ms on 1.25ms post 1.15ms diff 48.3µs
align 2147483648 pre 1.12ms on 1.12ms post 1.12ms diff 800ns
align 1073741824 pre 1.12ms on 1.12ms post 1.12ms diff 668ns
align 536870912 pre 1.12ms on 1.12ms post 1.12ms diff 414ns
align 268435456 pre 1.24ms on 1.25ms post 1.16ms diff 46.9µs
align 134217728 pre 1.24ms on 1.25ms post 1.16ms diff 44.8µs
align 67108864 pre 1.3ms on 1.34ms post 1.23ms diff 71.7µs
align 33554432 pre 1.3ms on 1.34ms post 1.23ms diff 71.5µs
align 16777216 pre 1.3ms on 1.33ms post 1.23ms diff 69.6µs
align 8388608 pre 1.28ms on 1.3ms post 1.18ms diff 72.1µs
align 4194304 pre 1.28ms on 1.3ms post 1.25ms diff 37µs **
align 2097152 pre 1.3ms on 1.34ms post 1.23ms diff 70.8µs
align 1048576 pre 1.3ms on 1.34ms post 1.23ms diff 70.7µs **
align 524288 pre 1.26ms on 1.26ms post 1.23ms diff 19.6µs
align 262144 pre 1.26ms on 1.26ms post 1.23ms diff 19.6µs
align 131072 pre 1.25ms on 1.26ms post 1.24ms diff 12.9µs
align 65536 pre 1.26ms on 1.26ms post 1.24ms diff 9.64µs **
align 32768 pre 1.26ms on 1.26ms post 1.22ms diff 18.8µs
align 16384 pre 1.26ms on 1.26ms post 1.23ms diff 18.7µs
align 8192 pre 1.26ms on 1.26ms post 1.23ms diff 19.4µs
align 4096 pre 1.23ms on 1.26ms post 1.23ms diff 35.3µs **
align 2048 pre 1.22ms on 1.26ms post 1.24ms diff 29.4µs
Analysis
- Results all over the place
- 4MB dip
- 1MB boundary has performance penalty = allocation unit?
- 64KB dip
- 4KB spike