[Jikesrvm-researchers] Root-tracing problem?

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We have made some changes to the jikes compliers and runtime in order to track 
the identities of methods performing allocation. Unfortunately, we have been 
getting some fairly non-deterministic errors. Surprisingly, these only arose 
with _213_javac (consistently) and mtrt (sometimes ran ok, somethings failed); 
other jvm98 benchmarks seemed to run ok.

We *believe* that the cause lies with tracing from roots - 
semiSpace.Plan.traceObject reports an address in an UNUSED_SPACE; we altered 
semiSpace.Plan.traceObject to tell us whether we were tracing from roots or 
not. We suspect that this is because we don't understand the GC maps 
sufficiently. We'd be grateful for any pointers, or indeed any suggestions on 
how best to hunt this bug other than insert sysWrite calls (which change the 
error reported!).

We are building and running on x86/linux.

Here's a typical error message:

Caching Off Speed = 100
======= _213_javac Starting =======
Run 0 start. Total memory=157286400 free memory=147648512
Javac benchmark starting...
Plan.traceObject spaceFailure from root
Plan.traceObject(): obj 0x9278febc or addr 0x9278fea8 of page 599951 is
in unknown space 127
Type = Ljava/lang/String;
: unknown space
-- Stack --
   Lcom/ibm/JikesRVM/VM; sysFail(Ljava/lang/String;)V at line 959
   Lcom/ibm/JikesRVM/memoryManagers/vmInterface/VM_Interface; 
sysFail(Ljava/lang/String;)V at line 1083
   Lcom/ibm/JikesRVM/memoryManagers/JMTk/BasePlan; 
spaceFailure(Lcom/ibm/JikesRVM/VM_Address;BLjava/lang/String;)V at line 877
   Lcom/ibm/JikesRVM/memoryManagers/JMTk/Plan; traceObject(Lcom/ibm/JikesRVM/VM_
Address;Z)Lcom/ibm/JikesRVM/VM_Address; at line 617
   Lcom/ibm/JikesRVM/memoryManagers/JMTk/BasePlan; 
traceObjectLocation(Lcom/ibm/JikesRVM/VM_Address;Z)V at line 291
   Lcom/ibm/JikesRVM/memoryManagers/JMTk/StopTheWorldGC; processAllWork()V at 
line 411
   Lcom/ibm/JikesRVM/memoryManagers/JMTk/StopTheWorldGC; collect()V at line 193
   Lcom/ibm/JikesRVM/memoryManagers/vmInterface/VM_CollectorThread; run()V at 
line 334
   Lcom/ibm/JikesRVM/VM_Thread; startoff()V at line 779
JikesRVM: exit 124

Here's a list of files we've modified and a brief indication of the changes 
made. One key change is that we push an extra integer in the code to allocate 
an object in rvm/src/vm/arch/intel/compilers/baseline/VM_Compiler.java, and 
ditto in the Call.mutateX calls in compilers/optimizing/ir/conversions/hir2lir/O
PT_ExpandRuntimeServices.java.

rvm/src/tools/bootImageRunner/sys.C
  - Added C code to output the actual trace.

rvm/src/vm/arch/intel/compilers/baseline/VM_Compiler.java
  - Added extra "aid" argument to:
     emit_resolved_new
     emit_unresolved_new
     emit_resolved_newarray
     emit_unresolved_newarray
     emit_multianewarray
  - Modified genMagic to pass a hardcoded aid to emit_resolved_newarray

rvm/src/vm/arch/intel/compilers/baseline/VM_MultianewarrayHelper.java
  - Added extra "aid" argument to newArrayArray and pass it though to
    VM_Runtime.buildMultiDimensionalArray

rvm/src/vm/VM_Configuration.java
  - Added a boolean MemTrace flag

rvm/src/vm/classLoader/VM_Array.java
  - Modified slowArrayCopy to pass an aid to VM_Runtime.resolvedNewArray

rvm/src/vm/compilers/baseline/VM_BaselineCompiler.java
  - Modified genCode case statement that handles JBC_new to pass an "aid" to
    emit_resolved_new and emit_unresolved_new
  - Modified genCode case statement that handles JBC_newarray to pass an "aid"
    to emit_resolved_newarray
  - Modified genCode case statement that handles JBC_anewarray to pass an
    "aid" to emit_resolved_newarray and emit_unresolved_newarray
  - Modified genCode case statement that handles JBC_multianewarray to pass
    an "aid" to emit_multianewarray
  - Added "aid" argument to the abstract methods:
      emit_resolved_new
      emit_unresolved_new
      emit_resolved_newarray
      emit_unresolved_newarray
      emit_multianewarray

rvm/src/vm/compilers/optimizing/ir/conversions/hir2lir/OPT_ExpandRuntimeServices
.java
  - Modified "perform" :
     NEW_opcode to pass "aid" to VM_Entrypoints.resolvedNewScalarMethod
     NEW_UNRESOLVED_opcode to pass "aid" to VM_Entrypoints.unresolvedNewScalarMe
thod
     NEWARRAY_opcode to pass "aid" to VM_Entrypoints.resolvedNewArrayMethod
     NEWARRAY_UNRESOLVED_opcode to pass "aid" to VM_Entrypoints.unresolvedNewArr
ayMethod
     NEWOBJMULTIARRAY_opcode to pass "aid" to VM_Entrypoints.optNewArrayArrayMet
hod

rvm/src/vm/compilers/optimizing/ir/instruction/InstructionFormatList.dat
  - Changed "Call" to generate code for upto 8 parameters instead of 7

rvm/src/vm/compilers/optimizing/vmInterface/services/VM_OptLinker.java
  - Added "aid" argument to newArrayArray, passes it to 
    VM_Runtime.buildMultiDimensionalArray

rvm/src/vm/jni/VM_JNIFunctions.java
  - Modified AllocObject method to pass an "aid" to
    VM_Runtime.resolvedNewScalar
  - Modified NewObjectArray method to pass an "aid" to 
    VM_Runtime.resolvedNewArray

rvm/src/vm/libSupport/java/lang/Class.java
  - Modified newInstance to pass "aid" to VM_Runtime.resolvedNewScalar

rvm/src/vm/libSupport/java/lang/reflect/Constructor.java
  - Modified newInstance to pass "aid" to VM_Runtime.resolvedNewScalar

rvm/src/vm/memoryManagers/JMTk/gcspy/drivers/SemiSpaceTraceDriver.java
  - Modifed "boot" to call VM_SysCall.memTraceBoot
  - Added "emitAlloc" method
  - Added "emitDeath" method

rvm/src/vm/memoryManagers/JMTk/plan/BasePlan.java
  - Added a MEM_TRACE flag

rvm/src/vm/memoryManagers/JMTk/utility/AllocAdvice.java
  - All new

rvm/src/vm/memoryManagers/JMTk/utility/CallSite.java
  - All new

rvm/src/vm/memoryManagers/JMTk/vmInterface/MM_Interface.java
  - Added "aid" argument to allocateScalar, passed to
    VM_ObjectModel.initializeScalar
  - Added "aid" argument to allocateArray, passed to 
    VM_ObjectModel.initializeArray
  - Modified cloneArray to pass an "aid" to allocateArray
  - Modified newStack to pass an "aid" to VM_ObjectModel.initializeArray
  - Modified newTIB to pass an "aid" to allocateArray

rvm/src/vm/memoryManagers/JMTk/vmInterface/VM_Interface.java
  - Added a "MemTrace" flag.

rvm/src/vm/objectModel/VM_MiscHeader.java
  - Added extra fields
  - Added an "aid" argument to initializeHeader, and the code to
    set the new fields of the header. Ditto for the boot image version
    of initializeHeader

rvm/src/vm/objectModel/VM_ObjectModel.java
  - Added an "aid" argument to initializeScalar, passed on to 
VM_MiscHeader.initializeHeader
  - Modified allocateScalar to pass an "aid" to VM_MiscHeader.initializeHeader
  - Added an "aid" argument to initializeArray, passed on to 
VM_MiscHeader.initializeHeader
  - Modified allocateArray to pass an "aid" to VM_MiscHeader.initializeHeader

rvm/src/vm/runtime/VM_BootRecord.java
  - Added hooks to C functions for output traces:
     memTraceBootIP
     memTraceBirthIP
     memTraceDeathIP
     memTraceTraceCommentIP
     memTraceMapIP
     memTraceMapCommentIP

rvm/src/vm/runtime/VM_Entrypoints.java
  - Added extra "aid" arguments to signatures of entrypoints:
     resolvedNewScalarMethod
     unresolvedNewScalarMethod
     unresolvedNewArrayMethod
     resolvedNewArrayMethod
     newArrayArrayMethod
     optNewArrayArrayMethod

rvm/src/vm/runtime/VM_Runtime.java
  - Added "aid" argument to unresolvedNewScalar, passed to resolvedNewScalar
  - Added "aid" argument to resolvedNewScalar, passed to resolvedNewScalar
  - Added "aid" argument to resolvedNewScalar, passed to 
MM_Interface.allocateScalar
  - Added "aid" argument to unresolvedNewArray, passed to resolvedNewArray
  - Added "aid" argument to resolvedNewArray, passed to resolvedNewArray
  - Added "aid" argument to resolvedNewArray, passed to 
MM_Interface.allocateArray
  - Modified clone to pass an "aid" to resolvedNewArray and resolvedNewScalar
  - Added "aid" argument to buildMultiDimensionalArray, passed to buildMDAHelper
  - Added "aid" argument to buildMDAHelper, passed to buildMDAHelper

rvm/src/vm/runtime/VM_SysCall.java
  - Added static method stubs for
      memTraceBoot
      memTraceBirth
      memTraceDeath
      memTraceTraceComment
      memTraceMap
      memTraceMapComment

rvm/src/tools/bootImageWriter/BootImageWriterConstants.java
  - Increased IMAGE_SIZE from 60 * 1024 * 1024 to 100 * 1024 * 1024

Richard Jones
Chris Ryder