why is cygwin so slow - linux

Question

I run a script on Ubuntu, and tested its time:
$ time ./merger
./merger 0.02s user 0.03s system 99% cpu 0.050 total
it spent less than 1 second.
but if I used cygwin:
$ time ./merger
real 3m22.407s
user 0m0.367s
sys 0m0.354s
It spent more than 3 minutes.
Why did this happen? What shall I do to increase the executing speed on cygwin?

Answer 1

As others have already mentioned, Cygwin's implementation of fork and process spawning on Windows in general are slow.
Using this fork() benchmark, I get following results:
rr-#cygwin:~$ ./test 1000
Forked, executed and destroyed 1000 processes in 5.660011 seconds.
rr-#arch:~$ ./test 1000
Forked, executed and destroyed 1000 processes in 0.142595 seconds.
rr-#debian:~$ ./test 1000
Forked, executed and destroyed 1000 processes in 1.141982 seconds.
Using time (for i in {1..10000};do cat /dev/null;done) to benchmark process spawning performance, I get following results:
rr-#work:~$ time (for i in {1..10000};do cat /dev/null;done)
(...) 19.11s user 38.13s system 87% cpu 1:05.48 total
rr-#arch:~$ time (for i in {1..10000};do cat /dev/null;done)
(...) 0.06s user 0.56s system 18% cpu 3.407 total
rr-#debian:~$ time (for i in {1..10000};do cat /dev/null;done)
(...) 0.51s user 4.98s system 21% cpu 25.354 total
Hardware specifications:
cygwin: Intel(R) Core(TM) i7-3770K CPU # 3.50GHz
arch: Intel(R) Core(TM) i7-4790K CPU # 4.00GHz
debian: Intel(R) Core(TM)2 Duo CPU T5270 # 1.40GHz
So as you see, no matter what you use, Cygwin will always operate worse. It loses hands down even to worse hardware (cygwin vs. debian in this benchmark, as per this comparison).