Ruby 2.2.0 Mashalling is slower than 2.1.5

Question

I have a complex object, my_object, which I marshaled with

Marshal.dump (my_object)

I compared the call performance of this line 100 times in both 2.1.5p273 and 2.2.0, and the results are below:

2.1.5 user system total real Marshal Dump 7.310000 0.120000 7.430000 ( 8.988470) Marshal Dump 7.520000 0.050000 7.570000 ( 8.210356) Marshal Dump 7.610000 0.050000 7.660000 ( 8.432685) 2.2.0 user system total real Marshal Dump 26.480000 0.150000 26.630000 ( 29.591742) Marshal Dump 24.100000 0.300000 24.400000 ( 28.520397) Marshal Dump 26.210000 0.210000 26.420000 ( 29.993412) 

(I ran the test 3 times for each version to be thorough.)

As you can see, it takes more than 3 times in 2.2.0 versus 2.1.5. I disabled Marshal.dump because, using ruby-prof gem, it showed me that it was a line that worked poorly; but I cannot find a way to get the methods that Marshal.dump itself calls in the profiler.

Edit: see my answer with minimal playback found after many experiments

Answer 1

Source location nil .

 Marshal.method(:dump).source_location #=> nil 

This means that it is an embedded C method, and there is no longer any Ruby code that you can trace. In other words, this is an atomic elementary method.

If you think your result is valid, I suggest you post it as an error in the Ruby trunk . For the newest versions of Ruby, several performance issues have indeed been found, so your case does not look unusual.

Answer 2

It orders floats, which slows down.

 require 'benchmark' class ToBeMarshaled def initialize n @a = [] n.times do |i| @a << i.to_f end end end tbm = ToBeMarshaled.new(10000) n = 100 Benchmark.bm do |x| x.report("Marshal Dump") {for i in 1..n; Marshal.dump(tbm); end} end 

(ran the test 3 times for each version of Ruby):

 2.1.5 user system total real Marshal Dump 0.640000 0.010000 0.650000 ( 0.744080) Marshal Dump 0.670000 0.000000 0.670000 ( 0.758597) Marshal Dump 0.650000 0.020000 0.670000 ( 0.747583) 2.2.0 user system total real Marshal Dump 25.070000 0.220000 25.290000 ( 27.980023) Marshal Dump 24.100000 0.160000 24.260000 ( 26.633049) Marshal Dump 24.440000 0.230000 24.670000 ( 27.540826) 

~ 35 times slower.

If you take ".to_f" from this code, you get:

 2.1.5 user system total real Marshal Dump 0.160000 0.000000 0.160000 ( 0.180247) Marshal Dump 0.180000 0.000000 0.180000 ( 0.189485) Marshal Dump 0.160000 0.010000 0.170000 ( 0.191304) 2.2.0 user system total real Marshal Dump 0.120000 0.010000 0.130000 ( 0.146710) Marshal Dump 0.130000 0.010000 0.140000 ( 0.159851) Marshal Dump 0.130000 0.000000 0.130000 ( 0.143917) 

2.2.0 slightly ends with 2.1.5.