Usage

$ make
$ dd if=/dev/zero of=X bs=256M count=1
$ ./write-bench <X >Y # Same as "cp X Y"

Notes

• The benchmark sleeps 0.1 seconds between all three runs
• Best run is displayed in the first column
• The file is read sequentially once prior to the benchmark
• Benchmark only measures the time to copy data to stdout
  • In particular, depending on filesystem, the next ftruncate(fd, 0) may take very long
  • No fsync() or fdatasync() is performed

Also see my blog post on the topic.

Some Results

Ext3+dmcrypt, SSD, filesize=256MB, kernel=3.13-1-amd64

pipe+splice + advices + trunc 371ms 385ms 2704ms
sendfile + advices + trunc 380ms 528ms 2910ms (+ 2.4%)
read+write 16bs + advices 384ms 414ms 425ms (+ 3.5%)
pipe+splice 389ms 403ms 1631ms (+ 4.9%)
sendfile 390ms 410ms 663ms (+ 5.1%)
read+write 256bs 393ms 634ms 806ms (+ 5.9%)
sendfile + advices 401ms 408ms 446ms (+ 8.1%)
pipe+splice + advices 403ms 416ms 417ms (+ 8.6%)
read+write 16bs 405ms 537ms 896ms (+ 9.2%)
read+write 4bs 413ms 427ms 638ms (+ 11.3%)
mmap+write + advices + trunc 414ms 449ms 755ms (+ 11.6%)
mmap+write + advices 432ms 458ms 740ms (+ 16.4%)
mmap+write 438ms 444ms 846ms (+ 18.1%)
read+write bs 469ms 538ms 901ms (+ 26.4%)
read+write 1k 639ms 672ms 866ms (+ 72.2%)
read+write 16bs + advices + trunc 1007ms 1500ms 4062ms (+ 171.4%)
sendfile + advices + falloc 1381ms 1486ms 1742ms (+ 272.2%)
mmap+write + advices + falloc 1405ms 1426ms 1576ms (+ 278.7%)
read+write 16bs + advices + falloc 1446ms 1524ms 1683ms (+ 289.8%)
pipe+splice + advices + falloc 1863ms 1909ms 1950ms (+ 402.2%)

XFS, SSD, filesize=1GB, kernel=2.6.32-5-amd64

sendfile + advices + falloc 398ms 405ms 406ms
pipe+splice + advices + falloc 407ms 409ms 409ms (+ 2.3%)
sendfile 445ms 448ms 459ms (+ 11.8%)
sendfile + advices 447ms 448ms 450ms (+ 12.3%)
pipe+splice 459ms 460ms 462ms (+ 15.3%)
pipe+splice + advices 460ms 460ms 467ms (+ 15.6%)
read+write 16bs + advices + falloc 464ms 465ms 466ms (+ 16.6%)
sendfile + advices + trunc 468ms 471ms 476ms (+ 17.6%)
pipe+splice + advices + trunc 471ms 472ms 476ms (+ 18.3%)
mmap+write + advices + falloc 482ms 483ms 485ms (+ 21.1%)
read+write 256bs 504ms 508ms 512ms (+ 26.6%)
read+write 16bs 505ms 506ms 507ms (+ 26.9%)
read+write 16bs + advices 511ms 515ms 528ms (+ 28.4%)
read+write 4bs 524ms 538ms 541ms (+ 31.7%)
mmap+write + advices 530ms 530ms 544ms (+ 33.2%)
mmap+write 530ms 533ms 533ms (+ 33.2%)
read+write 16bs + advices + trunc 537ms 540ms 543ms (+ 34.9%)
mmap+write + advices + trunc 557ms 563ms 564ms (+ 39.9%)
read+write bs 630ms 638ms 638ms (+ 58.3%)
read+write 1k 1138ms 1156ms 1168ms (+ 185.9%)

XFS, Hard Drive, filesize=1G, kernel=2.6.32-5-amd64

pipe+splice + advices + falloc 580ms 597ms 706ms
sendfile + advices + falloc 591ms 600ms 710ms (+ 1.9%)
pipe+splice + advices 624ms 699ms 766ms (+ 7.6%)
sendfile + advices 627ms 658ms 676ms (+ 8.1%)
pipe+splice 650ms 748ms 887ms (+ 12.1%)
sendfile 653ms 658ms 693ms (+ 12.6%)
read+write 16bs + advices + falloc 683ms 688ms 689ms (+ 17.8%)
sendfile + advices + trunc 685ms 686ms 825ms (+ 18.1%)
pipe+splice + advices + trunc 691ms 720ms 723ms (+ 19.1%)
read+write 16bs 718ms 742ms 753ms (+ 23.8%)
mmap+write + advices + falloc 733ms 733ms 820ms (+ 26.4%)
read+write 256bs 737ms 741ms 746ms (+ 27.1%)
read+write 16bs + advices 746ms 754ms 758ms (+ 28.6%)
read+write 4bs 759ms 774ms 817ms (+ 30.9%)
read+write 16bs + advices + trunc 774ms 775ms 780ms (+ 33.4%)
mmap+write 786ms 798ms 799ms (+ 35.5%)
mmap+write + advices + trunc 814ms 831ms 948ms (+ 40.3%)
mmap+write + advices 815ms 845ms 927ms (+ 40.5%)
read+write bs 856ms 889ms 905ms (+ 47.6%)
read+write 1k 1482ms 1497ms 1534ms (+ 155.5%)

tmpfs /dev/shm, filesize=256MB, kernel=3.13-1-amd64

sendfile + advices + trunc 132ms 133ms 133ms
sendfile 132ms 132ms 133ms (+ 0.0%)
sendfile + advices 133ms 134ms 134ms (+ 0.8%)
pipe+splice 133ms 134ms 134ms (+ 0.8%)
pipe+splice + advices + trunc 134ms 134ms 134ms (+ 1.5%)
pipe+splice + advices 134ms 134ms 135ms (+ 1.5%)
read+write 16bs + advices + trunc 135ms 136ms 137ms (+ 2.3%)
read+write 16bs + advices 135ms 136ms 136ms (+ 2.3%)
read+write 16bs 135ms 135ms 135ms (+ 2.3%)
read+write 256bs 137ms 137ms 138ms (+ 3.8%)
read+write 4bs 139ms 139ms 140ms (+ 5.3%)
sendfile + advices + falloc 140ms 140ms 141ms (+ 6.1%)
pipe+splice + advices + falloc 142ms 142ms 143ms (+ 7.6%)
read+write 16bs + advices + falloc 145ms 145ms 145ms (+ 9.8%)
read+write bs 154ms 155ms 155ms (+ 16.7%)
mmap+write + advices 169ms 170ms 170ms (+ 28.0%)
mmap+write 169ms 170ms 170ms (+ 28.0%)
mmap+write + advices + trunc 170ms 170ms 174ms (+ 28.8%)
mmap+write + advices + falloc 175ms 176ms 178ms (+ 32.6%)
read+write 1k 244ms 245ms 258ms (+ 84.8%)

NFS, filesize=1G, kernel=2.6.32-5-amd64

pipe+splice 448ms 508ms 564ms
sendfile 485ms 496ms 501ms (+ 8.3%)
sendfile + advices 495ms 508ms 569ms (+ 10.5%)
sendfile + advices + trunc 497ms 524ms 526ms (+ 10.9%)
pipe+splice + advices 512ms 528ms 542ms (+ 14.3%)
pipe+splice + advices + trunc 515ms 563ms 734ms (+ 15.0%)
sendfile + advices + falloc 546ms 596ms 18629ms (+ 21.9%)
read+write 16bs + advices + trunc 548ms 578ms 626ms (+ 22.3%)
read+write 4bs 560ms 583ms 649ms (+ 25.0%)
read+write 16bs + advices 561ms 597ms 599ms (+ 25.2%)
pipe+splice + advices + falloc 580ms 589ms 590ms (+ 29.5%)
read+write 16bs 605ms 610ms 638ms (+ 35.0%)
mmap+write + advices 610ms 637ms 807ms (+ 36.2%)
read+write 16bs + advices + falloc 614ms 652ms 652ms (+ 37.1%)
read+write bs 621ms 624ms 643ms (+ 38.6%)
mmap+write 637ms 640ms 657ms (+ 42.2%)
mmap+write + advices + trunc 639ms 655ms 658ms (+ 42.6%)
mmap+write + advices + falloc 667ms 672ms 699ms (+ 48.9%)
read+write 256bs 686ms 688ms 713ms (+ 53.1%)
read+write 1k 1638ms 1717ms 19303ms (+ 265.6%)

(Whole benchmark very slow because of synces: 0.16s user 47.74s system 2% cpu 30:21.46 total.)