JRuby

High CPU Loop with parallel Etc.group iterrations

Details

  • Type: Bug Bug
  • Status: Resolved Resolved
  • Priority: Major Major
  • Resolution: Fixed
  • Affects Version/s: JRuby 1.7.0.pre1
  • Fix Version/s: JRuby 1.7.0.pre2
  • Component/s: Standard Library
  • Labels:
    None
  • Environment:
    Mac OSX 10.6.8, JDK 7
  • Testcase included:
    yes
  • Number of attachments :
    1

Description

While browsing through the MRI source, I noticed the following code regarding Etc.group iteration:

etc.c
static void
each_group(void)
{
    if (group_blocking) {
	rb_raise(rb_eRuntimeError, "parallel group iteration");
    }
    group_blocking = (int)Qtrue;
    rb_ensure(group_iterate, 0, group_ensure, 0);
}

After running the attached test case, JRuby trunk goes into a high CPU loop. The C version prevents this by throwing a RuntimeError if you attempt a parallel loop. In essence the logic is:

  1. Check a group_blocking flag, and if it exists then throw a runtime error
  2. If it doesn't exist, set the flag to true
  3. Continue with the iteration

Activity

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Charles Oliver Nutter added a comment - 
commit 9e4e5d5884353751e0772eb8ce2a445fa98d0450
Author: Charles Oliver Nutter <headius@headius.com>
Date:   Thu Aug 2 12:43:07 2012 -0500

    Fix JRUBY-6056: High CPU Loop with parallel Etc.group iterrations
    
    Added the same check that MRI has here.

:100644 100644 5e82105... bacf230... M	src/org/jruby/ext/etc/RubyEtc.java
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Charles Oliver Nutter added a comment - commit 9e4e5d5884353751e0772eb8ce2a445fa98d0450 Author: Charles Oliver Nutter <headius@headius.com> Date: Thu Aug 2 12:43:07 2012 -0500 Fix JRUBY-6056: High CPU Loop with parallel Etc.group iterrations Added the same check that MRI has here. :100644 100644 5e82105... bacf230... M src/org/jruby/ext/etc/RubyEtc.java

People

  • Assignee:
    Charles Oliver Nutter
    Reporter:
    Chris White
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Dates

  • Created:
    Updated:
    Resolved: