Comparing speed of fread vs. read.table for reading the first 1M rows out of 100M

Question

I have a 14GB data.txt file. I was comparing the speed of fread and read.table by reading the first 1M rows. It looks like fread is mu

Answer 1

fread mmaps the file. This takes some time, and will map the whole file. This means subsequent "read-ins" will be faster.

read.table does not mmap the whole file. It can read in the file line by line [and stop at line 1000000].

You can see some background on mmap at mmap() vs. reading blocks

The examples in the help from fread highlight this behaiviour