[ruby-core:63165] [ruby-trunk - Bug #9934] [Closed] High memory usage from file_expand_path_*

Issue #9934 has been updated by Nobuyoshi Nakada.

Tracker changed from Backport to Bug
Project changed from Backport21 to ruby-trunk
Description updated
Category set to core
Status changed from Open to Closed
Target version set to current: 2.2.0
ruby -v set to current
Backport set to 2.0.0: REQUIRED, 2.1: REQUIRED

Don't move projects, update Backport instead.

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Bug #9934: High memory usage from file_expand_path_*
https://bugs.ruby-lang.org/issues/9934#change-47220

* Author: Aman Gupta
* Status: Closed
* Priority: Normal
* Assignee: 
* Category: core
* Target version: current: 2.2.0
* ruby -v: current
* Backport: 2.0.0: REQUIRED, 2.1: REQUIRED
----------------------------------------
All the file expansion routines use `EXPAND_PATH_BUFFER()` which allocates PATH_MAX bytes on the heap per invocation.
The strings returned by `File.expand_path` are never realloc'd after they are populated, so they continue using 4kb (on linux) per string.
In our rails app, 22MB of heap usage is due to expanded path name strings.

~~~
$ ruby -robjspace -e' puts ObjectSpace.dump(File.expand_path("/foo")) '
{"address":"0x007fa2b44dd6c8", "type":"STRING", "class":"0x007fa2b3f99608", "bytesize":4, "capacity":4098, "value":"/foo", "encoding":"US-ASCII", "memsize":4099, "flags":{"wb_protected":true}}
~~~

The following failing patch demonstrates the issue as well:

~~~diff
diff --git a/test/ruby/test_file_exhaustive.rb b/test/ruby/test_file_exhaustive.rb
index 2c945ea..49be9de 100644
--- a/test/ruby/test_file_exhaustive.rb
+++ b/test/ruby/test_file_exhaustive.rb
@@ -458,6 +458,12 @@ class TestFileExhaustive < Test::Unit::TestCase
     end
   end

+  def test_expand_path_memsize
+    require "objspace"
+    path = File.expand_path("/foo")
+    assert_equal 5, ObjectSpace.memsize_of(path)
+  end
+
   def test_expand_path_encoding
     drive = (DRIVE ? 'C:' : '')
     if Encoding.find("filesystem") == Encoding::CP1251
~~~



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