On 01/08/2014 07:30 AM, David Holmes wrote:
On 8/01/2014 4:19 PM, David Holmes wrote:
On 8/01/2014 7:33 AM, srikalyan chandrashekar wrote:
Hi David, TraceExceptions with fastdebug build produced some nice trace
<http://cr.openjdk.java.net/%7Esrikchan/OOME_exception_trace.log> . The
native method wait(long) is where the OOME if being thrown, the deepest
call is in

src/share/vm/gc_interface/collectedHeap.inline.hpp, line 157

Yes but it is the caller that is of interest:

Exception <a 'java/lang/OutOfMemoryError'> (0x00000000d6a01840)
thrown
[/HUDSON/workspace/8-2-build-linux-amd64/jdk8/1317/hotspot/src/share/vm/runtime/objectMonitor.cpp,
line 1649]
for thread 0x00007f78c40d2800
Exception <a 'java/lang/OutOfMemoryError'> (0x00000000d6a01840)
  thrown in interpreter method <{method} {0x00007f78b4800ae0} 'wait'
'(J)V' in 'java/lang/Object'>
  at bci 0 for thread 0x00007f78c40d2800

The ReferenceHandler thread gets the OOME trying to allocate the
InterruptedException.

However we already have a catch block around the wait() so how is this OOME getting through? A bug in exception handling in the interpreter ??


Might be. And it may have something to do with the fact that the Thread.run() method is the 1st call frame on the thread's stack (seems like corner case). The last few meaningful TraceExceptions records are:


Exception <a 'java/lang/OutOfMemoryError'> (0x00000000d6a01840)
thrown [/HUDSON/workspace/8-2-build-linux-amd64/jdk8/1317/hotspot/src/share/vm/gc_interface/collectedHeap.inline.hpp, line 157]
for thread 0x00007f78c40d2800
Exception <a 'java/lang/OutOfMemoryError'> (0x00000000d6a01840)
thrown [/HUDSON/workspace/8-2-build-linux-amd64/jdk8/1317/hotspot/src/share/vm/runtime/objectMonitor.cpp, line 1649]
for thread 0x00007f78c40d2800
Exception <a 'java/lang/OutOfMemoryError'> (0x00000000d6a01840)
thrown in interpreter method <{method} {0x00007f78b4800ae0} 'wait' '(J)V' in 'java/lang/Object'>
 at bci 0 for thread 0x00007f78c40d2800
Exception <a 'java/lang/OutOfMemoryError'> (0x00000000d6a01840)
thrown in interpreter method <{method} {0x00007f78b4800ca8} 'wait' '()V' in 'java/lang/Object'>
 at *bci 2* for thread 0x00007f78c40d2800
Exception <a 'java/lang/OutOfMemoryError'> (0x00000000d6a01840)
thrown in interpreter method <{method} {0x00007f78b48d2250} 'run' '()V' in 'java/lang/ref/Reference$ReferenceHandler'>
 at *bci 36* for thread 0x00007f78c40d2800


Here's the relevant bytecodes:


public class java.lang.Object

  public final void wait() throws java.lang.InterruptedException;
    descriptor: ()V
    flags: ACC_PUBLIC, ACC_FINAL
    Code:
      stack=3, locals=1, args_size=1
         0: aload_0
         1: lconst_0
*         2: invokevirtual #73                 // Method wait:(J)V*
         5: return
      LineNumberTable:
        line 502: 0
        line 503: 5
    Exceptions:
      throws java.lang.InterruptedException


class java.lang.ref.Reference$ReferenceHandler extends java.lang.Thread

  public void run();
    descriptor: ()V
    flags: ACC_PUBLIC
    Code:
      stack=2, locals=5, args_size=1
0: invokestatic #62 // Method java/lang/ref/Reference.access$100:()Ljava/lang/ref/Reference$Lock;
         3: dup
         4: astore_2
         5: monitorenter
6: invokestatic #61 // Method java/lang/ref/Reference.access$200:()Ljava/lang/ref/Reference;
         9: ifnull        33
12: invokestatic #61 // Method java/lang/ref/Reference.access$200:()Ljava/lang/ref/Reference;
        15: astore_1
        16: aload_1
17: invokestatic #64 // Method java/lang/ref/Reference.access$300:(Ljava/lang/ref/Reference;)Ljava/lang/ref/Reference; 20: invokestatic #63 // Method java/lang/ref/Reference.access$202:(Ljava/lang/ref/Reference;)Ljava/lang/ref/Reference;
        23: pop
        24: aload_1
        25: aconst_null
26: invokestatic #65 // Method java/lang/ref/Reference.access$302:(Ljava/lang/ref/Reference;Ljava/lang/ref/Reference;)Ljava/lang/ref/Reference;
        29: pop
        30: goto          52
33: invokestatic #62 // Method java/lang/ref/Reference.access$100:()Ljava/lang/ref/Reference$Lock; * 36: invokevirtual #59 // Method java/lang/Object.wait:()V*
        39: goto          43
        42: astore_3
        43: goto          47
        46: astore_3
        47: aload_2
        48: monitorexit
        49: goto          0
        52: aload_2
        53: monitorexit
        54: goto          64
        57: astore        4
        59: aload_2
        60: monitorexit
        61: aload         4
        63: athrow
        64: aload_1
        65: instanceof    #38                 // class sun/misc/Cleaner
        68: ifeq          81
        71: aload_1
        72: checkcast     #38                 // class sun/misc/Cleaner
75: invokevirtual #67 // Method sun/misc/Cleaner.clean:()V
        78: goto          0
        81: aload_1
82: getfield #57 // Field java/lang/ref/Reference.queue:Ljava/lang/ref/ReferenceQueue;
        85: astore_2
        86: aload_2
87: getstatic #58 // Field java/lang/ref/ReferenceQueue.NULL:Ljava/lang/ref/ReferenceQueue;
        90: if_acmpeq     99
        93: aload_2
        94: aload_1
95: invokevirtual #66 // Method java/lang/ref/ReferenceQueue.enqueue:(Ljava/lang/ref/Reference;)Z
        98: pop
        99: goto          0
      Exception table:
         from    to  target type
*            33    39    42   Class java/lang/OutOfMemoryError*
            33    43    46   Class java/lang/InterruptedException
             6    49    57   any
            52    54    57   any
            57    61    57   any
      StackMapTable: number_of_entries = 11
           frame_type = 0 /* same */
           frame_type = 253 /* append */
          offset_delta = 32
          locals = [ top, class java/lang/Object ]
             frame_type = 72 /* same_locals_1_stack_item */
            stack = [ class java/lang/OutOfMemoryError ]
             frame_type = 0 /* same */
             frame_type = 66 /* same_locals_1_stack_item */
            stack = [ class java/lang/InterruptedException ]
             frame_type = 0 /* same */
             frame_type = 255 /* full_frame */
            offset_delta = 4
locals = [ class java/lang/ref/Reference$ReferenceHandler, class java/lang/ref/Reference, class java/lang/Object ]
            stack = []
             frame_type = 255 /* full_frame */
            offset_delta = 4
locals = [ class java/lang/ref/Reference$ReferenceHandler, top, class java/lang/Object ]
            stack = [ class java/lang/Throwable ]
             frame_type = 255 /* full_frame */
            offset_delta = 6
locals = [ class java/lang/ref/Reference$ReferenceHandler, class java/lang/ref/Reference ]
            stack = []
             frame_type = 16 /* same */
             frame_type = 250 /* chop */
            offset_delta = 17

        LineNumberTable:
          line 136: 0
          line 137: 6
          line 138: 12
          line 139: 16
          line 140: 24
          line 157: 33
          line 158: 39
          line 159: 43
          line 160: 47
          line 162: 52
          line 165: 64
          line 166: 71
          line 167: 78
          line 170: 81
          line 171: 86
          line 172: 99
  }


... if I understand correctly the TraceExceptions' output, one record is printed for each abruptly completed method. The last record printed shows that Object.wait() method completed abruptly by throwing OOME. Even if the OOME was caught and ignored, we would still get this TraceExceptions record. Am I right? There's no record of abruptly terminated ReferenceHandler.run() method in the output. This might be because there's no method "calling" the ReferenceHandler.run() method, since it is the 1st method on the call-stack. Are you sure the output is from a failed test?

Can we make the following adjustment to the ReferenceHandler and see what gets printed and/or whether we still get uncaught OOME:


    private static class ReferenceHandler extends Thread {
    ...
        public void run() {
            runImpl();
        }

        private void runImpl() {
            // ... the content of the original run() method
        }
    ...




Regards, Peter

David

David
-----

------------------- Excerpt Begins ---------------------

147  if (!gc_overhead_limit_was_exceeded) {
148    // -XX:+HeapDumpOnOutOfMemoryError and -XX:OnOutOfMemoryError
support
149    report_java_out_of_memory("Java heap space");
150
151    if (JvmtiExport::should_post_resource_exhausted()) {
152      JvmtiExport::post_resource_exhausted(
153        JVMTI_RESOURCE_EXHAUSTED_OOM_ERROR |
JVMTI_RESOURCE_EXHAUSTED_JAVA_HEAP,
154        "Java heap space");
155    }
156
157    THROW_OOP_0(Universe::out_of_memory_error_java_heap());
158  } else {

------------------- Excerpt Ends ---------------------


Would be helpful if David/some one else in the team could explain the
latent aspects/probable cause.

---
Thanks
kalyan

On 01/06/2014 04:40 PM, David Holmes wrote:
Back from vacation ...

On 20/12/2013 4:49 PM, David Holmes wrote:
On 20/12/2013 12:57 PM, srikalyan chandrashekar wrote:
Hi David Thanks for your comments, the unguarded part(clean and
enqueue)
in the Reference Handler thread does not seem to create any new
objects,
so it is the application(the test in this case) which is adding
objects
to heap and causing the Reference Handler to die with OOME.

The ReferenceHandler thread can only get OOME if it allocates (directly
or indirectly) - so there has to be something in the unguarded part
that
causes this. Again it may be an implicit action in the VM - similar to
the class load issue for InterruptedException.

Run a debug VM with -XX:+TraceExceptions to see where the OOME is
triggered.

David
-----

David

I am still
unsure about the side effects of the code change and agree with your
thoughts(on memory exhaustion test's reliability).

PS: hotspot dev alias removed from CC.

--
Thanks
kalyan

On 12/19/13 5:08 PM, David Holmes wrote:
Hi Kalyan,

This is not a hotspot issue so I'm moving this to core-libs, please
drop hotspot from any replies.

On 20/12/2013 6:26 AM, srikalyan wrote:
Hi all,  I have been working on the bug JDK-8022321
<https://bugs.openjdk.java.net/browse/JDK-8022321> , this is a
sporadic
failure and the webrev is available here
http://cr.openjdk.java.net/~srikchan/Regression/JDK-8022321_OOMEInReferenceHandler-webrev/





I'm really not sure what to make of this. We have a test that
triggers
an out-of-memory condition but the OOME can actually turn up in the
ReferenceHandler thread causing it to terminate and the test to fail.
We previously accounted for the non-obvious occurrences of OOME
due to
the Object.wait and the possible need to load the
InterruptedException
class - but still the OOME can appear where we don't want it. So
finally you have just placed the whole for(;;) loop in a
try/catch(OOME) that ignores the OOME. I'm certain that makes the
test
happy, but I'm not sure it is really what we want for the
ReferenceHandler thread. If the OOME occurs while cleaning, or
enqueuing then we will fail to clean and/or enqueue but there
would be
no indication that has occurred and I think that is a bigger problem
than this test failing.

There may be no way to make this test 100% reliable. In fact I'd
suggest that no memory exhaustion test can be 100% reliable.

David

*
**"Root Cause:Still not known"*
2 places where there is a possibility for OOME
1) Cleaner.clean()
2) ReferenceQueue.enqueue()

1)  The cleanup code in turn has 2 places where there is potential
for
throwing OOME,
     a) thunk Thread which is run from clean() method. This
Runnable is
passed to Cleaner and appears in the following classes
         java/nio/DirectByteBuffer.java
         sun/misc/Perf.java
         sun/nio/fs/NativeBuffer.java
         sun/nio/ch/IOVecWrapper.java
         sun/misc/Cleaner/ExitOnThrow.java
However none of the above overridden implementations ever create an
object in the clean() code.
b) new PrivilegedAction created in try catch Exception block of
clean() method but for this object to be created and to be held
responsible for OOME an Exception(other than OOME) has to be thrown.

2) No new heap objects are created in the enqueue method nor
anywhere in
the deep call stack (VM.addFinalRefCount() etc) so this cannot be a
potential cause.

*Experimental change to java.lang.Reference.java* :
- Put one more guard (try catch with OOME block) in the Reference
Handler Thread which may give the Reference Handler a chance to
cleanup.
This is fixing the test failure (several 1000 runs with 0 failures)
- Without the above change the test fails atleast 3-5 times for
every
1000 run.

*PS*: The code change is to a very critical part of JDK and i am
fully
not aware of the consequences of the change, hence seeking expert
help
here. Appreciate your time and inputs towards this.




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