[ http://issues.apache.org/jira/browse/HARMONY-38?page=all ]
Tim Ellison resolved HARMONY-38:
--------------------------------
Resolution: Fixed
Paulex,
Fixed in NIO module at repo revision 372204
- com.ibm.platform.struct.AbstractMemorySpy.java
- com.ibm.platform.struct.RuntimeMemorySpy.java
Please check that this fully resolves the problem.
> com.ibm.platform.struct.AbstractMemorySpy doesn't actually autoFree native
> memory
> ---------------------------------------------------------------------------------
>
> Key: HARMONY-38
> URL: http://issues.apache.org/jira/browse/HARMONY-38
> Project: Harmony
> Type: Bug
> Components: Classlib
> Reporter: Paulex Yang
> Assignee: Tim Ellison
> Priority: Critical
> Attachments: Harmony38-AbstractMemorySpy-patch.txt,
> Harmony38-RuntimeMemorySpy-patch.txt
>
> com.ibm.platform.struct.IMemorySpy is a memory watcher, and the
> AbstractMemorySpy is a default implementation working with nio direct buffers
> to free the native memories when direct buffer instances are garbage
> collected. But currently its auto free donsn't work.
> Look inside the orphanedMemory(Object obj) method, the memory is freed only
> if the local variable wrapper can be found from the memoryInUse, a Map which
> records the native memories used by direct buffers, but actually it will be
> removed when autoFree(PlatfromAddress) is invoked. Checking the autoFree()
> reference, I found that all DirectByteBuffer will invoke autoFree() in
> constructor, which means no memory will be freed.
> A simple fix:
> modify the Ln 94 in autoFree() from:
> wrapper = (AddressWrapper) memoryInUse.remove(address);
> to:
> wrapper = (AddressWrapper) memoryInUse.get(address);
> and it should work.
> The steps to reproduce the bug:
> 1. Add the following line in the the Ln109, which indicates the memory is
> auto freed by AbstractMemorySpy
> System.out.println("MemorySpy autofree:"+wrapper.shadow);
> 2. Run the test below:
> public class MemorySpyTest {
> public static void main(String[] args) throws Exception {
> for (int i = 0; i < 1000; i++) {
> try{
> ByteBuffer buffer = ByteBuffer.allocateDirect(1024);
> buffer = null;
> }catch(Exception e){
> e.printStackTrace();
> }
> System.gc();
> }
> }
> Before modification: application exits silently.
> After modification, hundres of lines printed out, like this:
> .....
> MemorySpy autofree:PlatformAddress[9310024]
> MemorySpy autofree:PlatformAddress[9311056]
> MemorySpy autofree:PlatformAddress[9312088]
> MemorySpy autofree:PlatformAddress[9313120]
> MemorySpy autofree:PlatformAddress[9314152]
> MemorySpy autofree:PlatformAddress[9315184]
> MemorySpy autofree:PlatformAddress[9316216]
> MemorySpy autofree:PlatformAddress[9317248]
> .......
> Another possible pitfall in AbstractMemorySpy is it uses WeakReference and
> ReferenceQueue to get notification when the buffers are ready to be garbage
> collected. But it is not so safe yet to free the native memory, because the
> weakly-reachable object has its chance to be resurrected to
> strongly-reachable, if only some finalize() method doing this is executed. A
> safer solution is to use PhantomReference instead, because phantom-reachable
> object has no chance to survive. The only concern is the PhantomReference
> should be explicitly cleared by application, but that's OK because the
> orphanedMemory() method is a perfect candidate to do this.
> I will attach the patch soon.
--
This message is automatically generated by JIRA.
-
If you think it was sent incorrectly contact one of the administrators:
http://issues.apache.org/jira/secure/Administrators.jspa
-
For more information on JIRA, see:
http://www.atlassian.com/software/jira
