Question

First, I know that when copying a file, if the buffer size is bigger, the copying process will be faster.

The following ruby script used to write line-by-line (i.e. size of buffer will depends on the line length):

input,output = ARGV[0], ARGV[1]

f_in = File.open input, "r"
f_out = File.open output, "w"

f_in.each {|line| f_out << line}

f_in.close
f_out.close

Ruby Script VS to Linux cp command

I've tried to copy a two files of size (300, 400 MBs), and found the above script is even faster than the cp Linux command, notably faster.

How this could happen? I suppose the cp is fully optimized!

Was it helpful?

Solution

It's probably due disk caches, try running

echo 3 > /proc/sys/vm/drop_caches

to clear up the cache before running your benchmark :)

my guess is that they do should be very, very close, ofcourse cp should start copying some miliseconds faster than ruby.

OTHER TIPS

It probably is happening because of the file system disk cache inside the kernel.

I'm sure that if you repeat several times a cp command, timings will be different.

Use the time command (as a prefix) to benchmark and repeat the test several times.

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