Dmitry Potapov <dpotapov@xxxxxxxxx> writes:
> file size = 1Kb; Hashing 100000 files
> Before:
> 0.63user 0.86system 0:01.49elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
> 0inputs+0outputs (0major+100428minor)pagefaults 0swaps
> After:
> 0.54user 0.53system 0:01.07elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
> 0inputs+0outputs (0major+421minor)pagefaults 0swaps
>
> As you can see, in all tests the read() version performed better than
> mmap() though the difference decreases with increase of the file size.
> While for 1Kb files, the speed up is 39% (based on the elapsed time),
> it is mere 1% for 1Mb file size.
Sounds good. Summarizing your numbers,
1Kb 39.25%
2Kb 27.27%
4Kb 17.06%
8Kb 11.21%
16Kb 7.00%
32Kb 4.81%
64Kb 3.31%
128Kb 2.29%
256Kb 3.51%
512Kb 2.92%
1024Kb 1.14%
32*1024 sounds like a better cut-off to me. After that, doubling the size
does not get comparable gain, and numbers get unstable (notice the glitch
around 256kB).
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