Performance Comparison of mmap() versus read() versus fread()

This post has moved to eklausmeier.goip.de/blog/2016/02-03-performance-comparison-mmap-versus-read-versus-fread.

I recently read in Computers are *fast*! by Julia Evans about a comparison between fread() and mmap() suggesting that both calls deliver roughly the same performance. Unfortunately the codes mentioned there and referenced in bytesum.c for fread() and bytesum_mmap.c for mmap() do not really compare the same thing. The first adds size_t, the second adds up uint8_t. My computer showed that these programs do behave differently and therefore give different performance.

I reprogrammed the comparison adding read() to fread() and mmap(). The code is in GitHub. Compile with

cc -Wall -O3 tbytesum1.c -o tbytesum1

For this program the results are as follows: