From 381475f02e6b44ae729f9403637b30c445b622e5 Mon Sep 17 00:00:00 2001 From: Peter Zhu Date: Tue, 12 Apr 2022 09:18:41 -0400 Subject: Use an empty string when building File.expand_path MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Allocating a string of length MAXPATHLEN and then shrinking the string is inefficient when the resulting path is short. Preallocating a large string is also a problem for Variable Width Allocation since we can't easily downsize the capacity. I ran the following benchmark: ```ruby Benchmark.ips do |x| { "empty" => "", "short" => "a/" * 10, "medium" => "a/" * 100, "long" => "a/" * 500 }.each do |name, path| x.report(name) do |times| i = 0 while i < times File.expand_path(path) i += 1 end end end end ``` On this commit: ``` empty 97.486k (± 0.7%) i/s - 492.915k in 5.056507s short 96.026k (± 2.4%) i/s - 486.489k in 5.068966s medium 86.304k (± 1.3%) i/s - 435.336k in 5.045112s long 59.395k (± 1.7%) i/s - 302.175k in 5.089026s ``` On master: ``` empty 94.138k (± 1.4%) i/s - 472.158k in 5.016590s short 92.043k (± 1.4%) i/s - 468.180k in 5.087496s medium 84.910k (± 2.3%) i/s - 425.750k in 5.017007s long 61.503k (± 2.7%) i/s - 309.723k in 5.039429s ``` --- test/ruby/test_file_exhaustive.rb | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'test/ruby') diff --git a/test/ruby/test_file_exhaustive.rb b/test/ruby/test_file_exhaustive.rb index 9ca991373e..a4f968be5f 100644 --- a/test/ruby/test_file_exhaustive.rb +++ b/test/ruby/test_file_exhaustive.rb @@ -874,7 +874,8 @@ class TestFileExhaustive < Test::Unit::TestCase path = File.expand_path("/foo") assert_operator(ObjectSpace.memsize_of(path), :<=, path.bytesize + GC::INTERNAL_CONSTANTS[:BASE_SLOT_SIZE], bug9934) path = File.expand_path("/a"*25) - assert_equal(path.bytesize + 1 + GC::INTERNAL_CONSTANTS[:BASE_SLOT_SIZE], ObjectSpace.memsize_of(path), bug9934) + assert_operator(ObjectSpace.memsize_of(path), :<=, + (path.bytesize + 1) * 2 + GC::INTERNAL_CONSTANTS[:BASE_SLOT_SIZE], bug9934) end def test_expand_path_encoding -- cgit v1.2.1