From 02629a59fc8b0b91b719b9298eb91f657ef30d3c Mon Sep 17 00:00:00 2001
From: Shizuo Fujita <fujita@clear-code.com>
Date: Mon, 16 Mar 2026 10:13:05 +0900
Subject: [PATCH] benchmark: Use IO#size instead of File.size to speed up file
 generation on Windows (#5277)
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**Which issue(s) this PR fixes**:
Fixes #

**What this PR does / why we need it**:
Using `File.size(path)` in a tight loop is very slow, especially on
Windows,
because it resolves the path and calls `stat` every time.

* benchmark code
```ruby
require 'bundler/inline'
gemfile do
  source 'https://rubygems.org'
  gem 'benchmark-ips'
end

FILE_PATH = "dummy_file.txt"

File.open(FILE_PATH, "w") do |f|
  Benchmark.ips do |x|
    x.time = 10

    x.report("File.size(path)") { File.size(FILE_PATH) }
    x.report("File#size") { f.size }
  end
end
```

* result
```
ruby 4.0.1 (2026-01-13 revision e04267a14b) +PRISM [x64-mingw-ucrt]
Warming up --------------------------------------
     File.size(path)     3.104k i/100ms
           File#size    17.874k i/100ms
Calculating -------------------------------------
     File.size(path)     31.099k (± 1.5%) i/s   (32.16 μs/i) -    313.504k in  10.083209s
           File#size    182.821k (± 1.4%) i/s    (5.47 μs/i) -      1.841M in  10.072168s
```

Using the instance method `IO#size` (f.size) avoids this overhead and
speeds up the 1GB test file generation by about 5x (from ~45s to ~9s) in

https://github.com/fluent/fluentd/blob/b819ccf772e1036adb17f49682c6b7053713066d/tasks/benchmark.rb#L13-L23

**Docs Changes**:
N/A

**Release Note**:
N/A

Signed-off-by: Shizuo Fujita <fujita@clear-code.com>
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
---
 tasks/benchmark.rb | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tasks/benchmark.rb b/tasks/benchmark.rb
index 930d9087cf..5eb3ead9a3 100644
--- a/tasks/benchmark.rb
+++ b/tasks/benchmark.rb
@@ -17,7 +17,7 @@
 
       loop do
         f.puts data
-        break if File.size(BENCHMARK_FILE_PATH) > BENCHMARK_FILE_SIZE
+        break if f.size > BENCHMARK_FILE_SIZE
       end
     end
   end