From: janmayjuldec-programming@...
Date: 2015-01-21T16:15:01+00:00
Subject: [ruby-core:67728] [ruby-trunk - Bug #10761] Marshal.dump 100%	slower in 2.2.0 vs 2.1.5

Issue #10761 has been updated by David Jenkins.


Final repro, no data files, all code:

~~~
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

~~~

results (ran benchmark 3 times for each Ruby version):

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

----------------------------------------
Bug #10761: Marshal.dump 100% slower in 2.2.0 vs 2.1.5
https://bugs.ruby-lang.org/issues/10761#change-51158

* Author: David Jenkins
* Status: Open
* Priority: High
* Assignee: 
* ruby -v: 2.2.0
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN
----------------------------------------
Calling Marshal.dump on a complex (nested) object 100 times shows the following: 

2.1.5
       		  user     system      total        real
Marshal Dump 24.350000   0.250000  24.600000 ( 29.330294)

2.2.0
                  user     system      total        real
Marshal Dump 50.450000   0.140000  50.590000 ( 52.268773)

To reproduce, put marshal_slow.rb and nested_ds.txt in same directory and run marshal_slow.rb.

I found that Marshal.dump only shows this kind of discrepancy on deeply nested objects.  The nested_ds.txt file is a dump of an object that contained a collection of sub objects of the same type.

---Files--------------------------------
nested_ds.txt (2.1 MB)
marshal_slow.rb (212 Bytes)
dataset_dump.txt (362 KB)
better_slow_marshal.rb (239 Bytes)


-- 
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