8342857: SA: Heap iterator makes incorrect assumptions about TLAB layout

Reviewed-by: cjplummer, rkennke, lmesnik

Author: stefank

src/hotspot/share/gc/shared/vmStructs_gc.hpp

@@ -91,6 +91,7 @@
   nonstatic_field(CardTableBarrierSet,         _defer_initial_card_mark,                      bool)                                  \
   nonstatic_field(CardTableBarrierSet,         _card_table,                                   CardTable*)                            \
                                                                                                                                      \
+     static_field(CollectedHeap,               _lab_alignment_reserve,                        size_t)                                \
   nonstatic_field(CollectedHeap,               _reserved,                                     MemRegion)                             \
   nonstatic_field(CollectedHeap,               _is_stw_gc_active,                             bool)                                  \
   nonstatic_field(CollectedHeap,               _total_collections,                            unsigned int)                          \

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/runtime/ThreadLocalAllocBuffer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2024, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -75,11 +75,11 @@ private long alignmentReserve() {
   }
 
   private long endReserve() {
-    long minFillerArraySize = Array.baseOffsetInBytes(BasicType.T_INT);
+    long labAlignmentReserve = VM.getVM().getLabAlignmentReserve();
     long reserveForAllocationPrefetch = VM.getVM().getReserveForAllocationPrefetch();
     long heapWordSize = VM.getVM().getHeapWordSize();
 
-    return Math.max(minFillerArraySize, reserveForAllocationPrefetch * heapWordSize);
+    return Math.max(labAlignmentReserve, reserveForAllocationPrefetch) * heapWordSize;
   }
 
   /** Support for iteration over heap -- not sure how this will

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/runtime/VM.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2024, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -127,6 +127,7 @@ public class VM {
   private ReversePtrs  revPtrs;
   private VMRegImpl    vmregImpl;
   private int          reserveForAllocationPrefetch;
+  private int          labAlignmentReserve;
 
   // System.getProperties from debuggee VM
   private Properties   sysProps;
@@ -138,12 +139,12 @@ public class VM {
   private Flag[] commandLineFlags;
   private Map<String, Flag> flagsMap;
 
-  private static Type intType;
-  private static Type uintType;
-  private static Type intxType;
-  private static Type uintxType;
-  private static Type sizetType;
-  private static Type uint64tType;
+  private static CIntegerType intType;
+  private static CIntegerType uintType;
+  private static CIntegerType intxType;
+  private static CIntegerType uintxType;
+  private static CIntegerType sizetType;
+  private static CIntegerType uint64tType;
   private static CIntegerType boolType;
   private Boolean sharingEnabled;
   private Boolean compressedOopsEnabled;
@@ -432,17 +433,29 @@ private VM(TypeDataBase db, JVMDebugger debugger, boolean isBigEndian) {
        vmRelease = CStringUtilities.getString(releaseAddr);
        Address vmInternalInfoAddr = vmVersion.getAddressField("_s_internal_vm_info_string").getValue();
        vmInternalInfo = CStringUtilities.getString(vmInternalInfoAddr);
-
-       Type threadLocalAllocBuffer = db.lookupType("ThreadLocalAllocBuffer");
-       CIntegerType intType = (CIntegerType) db.lookupType("int");
-       CIntegerField reserveForAllocationPrefetchField = threadLocalAllocBuffer.getCIntegerField("_reserve_for_allocation_prefetch");
-       reserveForAllocationPrefetch = (int)reserveForAllocationPrefetchField.getCInteger(intType);
     } catch (Exception exp) {
        throw new RuntimeException("can't determine target's VM version : " + exp.getMessage());
     }
 
     checkVMVersion(vmRelease);
 
+    // Initialize common primitive types
+    intType = (CIntegerType) db.lookupType("int");
+    uintType = (CIntegerType) db.lookupType("uint");
+    intxType = (CIntegerType) db.lookupType("intx");
+    uintxType = (CIntegerType) db.lookupType("uintx");
+    sizetType = (CIntegerType) db.lookupType("size_t");
+    uint64tType = (CIntegerType) db.lookupType("uint64_t");
+    boolType = (CIntegerType) db.lookupType("bool");
+
+    Type threadLocalAllocBuffer = db.lookupType("ThreadLocalAllocBuffer");
+    CIntegerField reserveForAllocationPrefetchField = threadLocalAllocBuffer.getCIntegerField("_reserve_for_allocation_prefetch");
+    reserveForAllocationPrefetch = (int)reserveForAllocationPrefetchField.getCInteger(intType);
+
+    Type collectedHeap = db.lookupType("CollectedHeap");
+    CIntegerField labAlignmentReserveField = collectedHeap.getCIntegerField("_lab_alignment_reserve");
+    labAlignmentReserve = (int)labAlignmentReserveField.getCInteger(sizetType);
+
     invocationEntryBCI = db.lookupIntConstant("InvocationEntryBci").intValue();
 
     // We infer the presence of JVMTI from the presence of the InstanceKlass::_breakpoints field.
@@ -493,14 +506,6 @@ private VM(TypeDataBase db, JVMDebugger debugger, boolean isBigEndian) {
     Flags_WAS_SET_ON_COMMAND_LINE = db.lookupIntConstant("JVMFlag::WAS_SET_ON_COMMAND_LINE").intValue();
     oopSize  = db.lookupIntConstant("oopSize").intValue();
 
-    intType = db.lookupType("int");
-    uintType = db.lookupType("uint");
-    intxType = db.lookupType("intx");
-    uintxType = db.lookupType("uintx");
-    sizetType = db.lookupType("size_t");
-    uint64tType = db.lookupType("uint64_t");
-    boolType = (CIntegerType) db.lookupType("bool");
-
     minObjAlignmentInBytes = getObjectAlignmentInBytes();
     if ((minObjAlignmentInBytes & (minObjAlignmentInBytes - 1)) != 0) {
       throw new RuntimeException("Object alignment " + minObjAlignmentInBytes + " is not power of two");
@@ -929,6 +934,10 @@ public int getReserveForAllocationPrefetch() {
     return reserveForAllocationPrefetch;
   }
 
+  public int getLabAlignmentReserve() {
+    return labAlignmentReserve;
+  }
+
   public boolean isSharingEnabled() {
     if (sharingEnabled == null) {
         Address address = VM.getVM().getDebugger().lookup(null, "UseSharedSpaces");