[#106355] [Ruby master Bug#18373] RBS build failure: '/include/x86_64-linux/ruby/config.h', needed by 'constants.o'. — "vo.x (Vit Ondruch)" <noreply@...>
Issue #18373 has been reported by vo.x (Vit Ondruch).
28 messages
2021/12/01
[ruby-core:106910] [Ruby master Bug#18447] Potential performance regression with String#lines in large strings
From:
"ttilberg (Tim Tilberg)" <noreply@...>
Date:
2021-12-29 21:54:49 UTC
List:
ruby-core #106910
Issue #18447 has been updated by ttilberg (Tim Tilberg).
Thanks everyone! I wondered if it wasn't due to memory allocations, but the "build a massive string" operation was successful and quite fast. I looked through `rb_str_enumerate_lines` in the C source, and got lost rather quickly, aside from seeing that if the string wasn't frozen, we would create a new one that _is_ frozen. I'm curious if someone would bother to take a moment to share where this was manifested from my example (`String#lines`)? I'm working my way up towards understanding Ruby at a deeper level.
Regardless, thank you everyone for triaging and creating a patch so quickly!
----------------------------------------
Bug #18447: Potential performance regression with String#lines in large strings
https://bugs.ruby-lang.org/issues/18447#change-95730
* Author: ttilberg (Tim Tilberg)
* Status: Closed
* Priority: Normal
* Assignee: peterzhu2118 (Peter Zhu)
* ruby -v: ruby 3.1.0p0 (2021-12-25 revision fb4df44d16) [x86_64-darwin20]
* Backport: 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
I believe there may be a potential performance regression regarding `String#lines` worth noting between 3.0.3 and 3.1.0. This came about in [this discussion](https://www.reddit.com/r/ruby/comments/rpje0g/fast_to_way_to_parse_csv/hqadqsd/) regarding large file parsing performance. We were benchmarking various ways to parse a 10 million row CSV file. Slurping the file took significantly longer than streaming in version 3.1.0, even though the data was able to fit in memory. After further research, we started to feel that there may be something to speak up about here, and I think it's pinned down to `String#lines`.
I'm running Mac OS Big Sur 11.6.1 on a 13" 2020 MBP with 32 GB ram. Specific Ruby versions are included in the comparison examples below.
The simplest reproduction seems to be:
Ruby 3.0.3: ~1.5 seconds
```
笆カ time ruby -ve '("\n" * 10_000_000).lines'
ruby 3.0.3p157 (2021-11-24 revision 3fb7d2cadc) [x86_64-darwin20]
ruby -ve '("\n" * 10_000_000).lines' 1.38s user 0.39s system 100% cpu 1.756 total
```
Ruby 3.1.0: ~11.5 seconds
```
笆カ time ruby -ve '("\n" * 10_000_000).lines'
ruby 3.1.0p0 (2021-12-25 revision fb4df44d16) [x86_64-darwin20]
ruby -ve '("\n" * 10_000_000).lines' 1.52s user 10.01s system 99% cpu 11.579 total
```
Some other observations:
An earlier script that I ran ruby-prof against looked like:
```
puts File.read("sample-data.csv").lines.sum { 1 }
```
- It appeared that the time increase stemmed from `String#lines`, as all other methods had similar time taken between the versions:
```
Ruby 3.1.0
%self total self wait child calls name
89.93 12.728 12.728 0.000 0.000 1 String#lines
9.01 1.275 1.275 0.000 0.000 1 Array#sum
1.05 0.149 0.149 0.000 0.000 1 <Class::IO>#read
Ruby 3.0.3
%self total self wait child calls name
74.91 3.773 3.773 0.000 0.000 1 String#lines
22.15 1.116 1.116 0.000 0.000 1 Array#sum
2.93 0.148 0.148 0.000 0.000 1 <Class::IO>#read
```
- A similar enumerator without `String#lines` does not appear to cause this:
```
笆カ time ruby -ve '10_000_000.times.map { nil }'
ruby 3.0.3p157 (2021-11-24 revision 3fb7d2cadc) [x86_64-darwin20]
ruby -ve '10_000_000.times.map { nil }' 0.57s user 0.16s system 102% cpu 0.710 total
```
```
笆カ time ruby -ve '10_000_000.times.map { nil }'
ruby 3.1.0p0 (2021-12-25 revision fb4df44d16) [x86_64-darwin20]
ruby -ve '10_000_000.times.map { nil }' 0.61s user 0.16s system 102% cpu 0.753 total
```
- It doesn't seem related to string generation:
```
笆カ time ruby -ve '("\n" * 10_000_000)'
ruby 3.0.3p157 (2021-11-24 revision 3fb7d2cadc) [x86_64-darwin20]
-e:1: warning: possibly useless use of * in void context
ruby -ve '("\n" * 10_000_000)' 0.13s user 0.14s system 107% cpu 0.246 total
```
```
笆カ time ruby -ve '("\n" * 10_000_000)'
ruby 3.1.0p0 (2021-12-25 revision fb4df44d16) [x86_64-darwin20]
-e:1: warning: possibly useless use of * in void context
ruby -ve '("\n" * 10_000_000)' 0.13s user 0.14s system 107% cpu 0.245 total
```
(Thanks to simpl1g for the discussion on Reddit, and help detecting this potential issue)
--
https://bugs.ruby-lang.org/
Unsubscribe: <mailto:[email protected]?subject=unsubscribe>
<http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>