[erlang-bugs] Erlang 18.0-rc1 is behaving slower than 17.4 (and 17.5)

[José Valim]

Ok, I have run some more experiments.

*1. The time to start and shutdown the erlang system is higher on 18.0*

$ time erl -s erlang halt
real 0m0.357s
user 0m0.229s
sys 0m0.102s

Takes on average 0.35s on 18.0 but 0.25 on 17.3.

*2. The time to start, write to stdio and shutdown the erlang system is
higher on 18.0*

$ time erl -eval "io:format(hello, []), halt()."
real 0m0.512s
user 0m0.383s
sys 0m0.118s

Takes on average 0.51s on 18.0 but 0.28s on 17.3.

*3. The emulator in 18.0 takes considerably more memory than 17.3*

After running observer:start() on both, 18.0 takes 55MB while 17.3 takes
only 18MB.

*4. Time required to compile modules is higher on 18.0*

Given the sample code in this module:
https://gist.github.com/josevalim/bd0e82d9bfaf37599b9c

Then compile the module and run foo:start() in the shell after boot:

$ erlc foo.erl
$ erl
erl> foo:start().
Time: 1136296.

The timer:tc/2 result is on average 1.1s on 18.0 but 0.9s on 17.3.

*5. Time to compile a module and write to stdout with -s is very high on
18.0*

I have found this one by accident. If we invoke the gist above from the
command line, sometimes it takes about 8s to compile all modules and print
to terminal on 18.0. Just run the code above as:

$ erlc foo.erl && erl -s foo
erl> Time: 7803694.

It takes on average 0.9s on 17.3 but often it takes 7.8s on 18.0.

*Info*

Using Mac OS X, both Erlang compiled with .kerl using the same options.
Those results have been confirmed by other users running on different
machines.

I can continue running more of those experiments or I can try anything
specific. Just let me know.

*José Valim*
www.plataformatec.com.br
Skype: jv.ptec
Founder and Lead Developer
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