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Date: Wed, 9 Aug 2006 13:38:27 -0700 (PDT)
From: "Andrey Chernyshev (JIRA)" <jira@apache.org>
To: harmony-commits@incubator.apache.org
Subject: [jira] Created: (HARMONY-1125) [DRLVM] Thread Manager component
 contribution
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[DRLVM] Thread Manager component contribution
---------------------------------------------

                 Key: HARMONY-1125
                 URL: http://issues.apache.org/jira/browse/HARMONY-1125
             Project: Harmony
          Issue Type: Improvement
          Components: Contributions
            Reporter: Andrey Chernyshev


This patch is an improvement for DRLVM which consolidates it's threading 
subsystem into a single component - Thread Manager.

The attached bundle consists of two parts:
1) ThreadManager-09-08e.zip
        - Thread Manager code, tests and documentation 
          (it has to be unzipped into drlvm/trunk directory)

2) DRLVM-update-for-new-ThreadManager-09-08e.diff
        - Patch that integrates Thread Manager into DRLVM.

The primary purpose of this update is to make a step toward archiving a 
better modularity within the DRLVM, as well as do some enhancements over 
its threading subsystem. This is the result of refactoring of the 
threading-related code in the DRLVM into a separate library which 
is now implemented on top of the Apache Porting Layer.

Here is the summary of enhancements that were made:
- Threading becomes a modular component in JVM with a well-defined interface 
  (one may try playing now with the different threading implementations without 
   rewriting random pieces of the drlvm code);
- Thread Manager is implemented on top of APR which may help to simplify 
  it's porting to other platforms (the only platform dependent piece is JIT helpers)
- Java monitors are reimplemented such that:
    - Performance is improved with help of the lock reservation algorithm 
      (see http://portal.acm.org/citation.cfm?id=582433)
    - Recursion overflow condition is now handled correctly 
- Thread creation overhead is decreased;
- Java threads now are always created at the single place; 
- Miscellaneous threading bugs went away, for example: hangs during thread stress tests, 
  crashes on sleep(), incorrect reporting of JVMTI state and others.

Note that the low-level (or "native") interface of the Thread Manager 
has been designed to be hythread-compatible with the intent of having 
classlib and DRLVM sharing the same threading library. It also adds
a certain extensions to the original hythread which were required by
drlvm (located in hythread_ext.h). However, these functions can still 
be easily renamed from hythread_* to something else if people believe 
this idea is wrong.

Thread Manager comes with the extensive documentation which uncovers some 
of the details of the DRLVM's threading subsystem (you may find it at vm/thread/doc/ThreadManager.htm).
There is also a set of unit tests for Thread Manager (located at vm/tests/unit) 
those framework can probably be used for the further unit tests development for 
other modules in DRLVM.

The integration patch consists of the following pieces:

build/make/* - changes necessary to include unit tests and accommodate 
               new threading structure

build/patches/*/APR - quick fixes to a few bugs in the APR: apr_thread_cond 
               on Windows, apr_thread_yield on Linux.
               Note that the Thread Manager implementation requires a certain 
               funct-ty which appeared to be beyond the APR, these additional
               functions were added for now at vm\port\include\apr_thread_ext.h:
                  apr_thread_set_priority()
                  apr_memory_rw_barrier()
                  apr_thread_yield_other()
                  apr_thread_times()
                  apr_thread_cancel()
               If we find this code useful we may try proposing them
               back to the APR project.

vm/vmcore/src/thread/*  - These files contained old threading code which is now 
               either completely removed or re-mapped into new Thread Manager.
               	
vm/vmcore/src/thread/hythr/
             - it was "hythread" emulation library, now it is replaced with the 
               more funcitonal "native" layer of the Thread Manager (which still
               implements the most of hythread_* API).

vm/port/src/encoder/* - added support for ROR instruction to the encoder

Other changes were done as required to replace the references to the old threading code
with the calls/references to the new Thread Manager.


Thank you,
Andrey Chernyshev
Intel Middleware Products Division


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