[ruby-core:67724] [ruby-trunk - Bug #10761] Marshal.dump 100% slower in 2.2.0 vs 2.1.5

Issue #10761 has been updated by David Jenkins.

File dataset_dump.txt added
File better_slow_marshal.rb added

I have an even better repro (attached) which yielded the following results:

2.1.5
                  user     system      total        real
Marshal Dump  4.250000   0.080000   4.330000 (  4.682933)
Marshal Dump  4.440000   0.040000   4.480000 (  4.613776)
Marshal Dump  4.500000   0.050000   4.550000 (  4.717084)

2.2.0
                  user     system      total        real
Marshal Dump 13.390000   0.070000  13.460000 ( 13.742177)
Marshal Dump 14.540000   0.090000  14.630000 ( 14.884479)
Marshal Dump 13.580000   0.060000  13.640000 ( 13.968422)


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Bug #10761: Marshal.dump 100% slower in 2.2.0 vs 2.1.5
https://bugs.ruby-lang.org/issues/10761#change-51151

* 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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