--- a/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp	Mon Aug 01 10:04:28 2011 -0700
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp	Tue Aug 02 12:13:13 2011 -0700
@@ -1901,12 +1901,27 @@
   PermanentGenerationSpec* pgs = collector_policy()->permanent_generation();
   // Includes the perm-gen.
 
-  const size_t total_reserved = max_byte_size + pgs->max_size();
+  // When compressed oops are enabled, the preferred heap base
+  // is calculated by subtracting the requested size from the
+  // 32Gb boundary and using the result as the base address for
+  // heap reservation. If the requested size is not aligned to
+  // HeapRegion::GrainBytes (i.e. the alignment that is passed
+  // into the ReservedHeapSpace constructor) then the actual
+  // base of the reserved heap may end up differing from the
+  // address that was requested (i.e. the preferred heap base).
+  // If this happens then we could end up using a non-optimal
+  // compressed oops mode.
+
+  // Since max_byte_size is aligned to the size of a heap region (checked
+  // above), we also need to align the perm gen size as it might not be.
+  const size_t total_reserved = max_byte_size +
+                                align_size_up(pgs->max_size(), HeapRegion::GrainBytes);
+  Universe::check_alignment(total_reserved, HeapRegion::GrainBytes, "g1 heap and perm");
+
   char* addr = Universe::preferred_heap_base(total_reserved, Universe::UnscaledNarrowOop);
 
-  ReservedSpace heap_rs(max_byte_size + pgs->max_size(),
-                        HeapRegion::GrainBytes,
-                        UseLargePages, addr);
+  ReservedHeapSpace heap_rs(total_reserved, HeapRegion::GrainBytes,
+                            UseLargePages, addr);
 
   if (UseCompressedOops) {
     if (addr != NULL && !heap_rs.is_reserved()) {
@@ -1914,14 +1929,17 @@
       // region is taken already, for example, by 'java' launcher.
       // Try again to reserver heap higher.
       addr = Universe::preferred_heap_base(total_reserved, Universe::ZeroBasedNarrowOop);
-      ReservedSpace heap_rs0(total_reserved, HeapRegion::GrainBytes,
-                             UseLargePages, addr);
+
+      ReservedHeapSpace heap_rs0(total_reserved, HeapRegion::GrainBytes,
+                                 UseLargePages, addr);
+
       if (addr != NULL && !heap_rs0.is_reserved()) {
         // Failed to reserve at specified address again - give up.
         addr = Universe::preferred_heap_base(total_reserved, Universe::HeapBasedNarrowOop);
         assert(addr == NULL, "");
-        ReservedSpace heap_rs1(total_reserved, HeapRegion::GrainBytes,
-                               UseLargePages, addr);
+
+        ReservedHeapSpace heap_rs1(total_reserved, HeapRegion::GrainBytes,
+                                   UseLargePages, addr);
         heap_rs = heap_rs1;
       } else {
         heap_rs = heap_rs0;

--- a/hotspot/src/share/vm/runtime/virtualspace.cpp	Mon Aug 01 10:04:28 2011 -0700
+++ b/hotspot/src/share/vm/runtime/virtualspace.cpp	Tue Aug 02 12:13:13 2011 -0700
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2011, 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
@@ -68,7 +68,7 @@
   assert(len >= required_size, "len too small");
 
   const size_t s = size_t(addr);
-  const size_t beg_ofs = s + prefix_size & suffix_align - 1;
+  const size_t beg_ofs = (s + prefix_size) & (suffix_align - 1);
   const size_t beg_delta = beg_ofs == 0 ? 0 : suffix_align - beg_ofs;
 
   if (len < beg_delta + required_size) {
@@ -113,8 +113,8 @@
     assert(res >= raw, "alignment decreased start addr");
     assert(res + prefix_size + suffix_size <= raw + reserve_size,
            "alignment increased end addr");
-    assert((res & prefix_align - 1) == 0, "bad alignment of prefix");
-    assert((res + prefix_size & suffix_align - 1) == 0,
+    assert((res & (prefix_align - 1)) == 0, "bad alignment of prefix");
+    assert(((res + prefix_size) & (suffix_align - 1)) == 0,
            "bad alignment of suffix");
   }
 #endif
@@ -135,7 +135,7 @@
     assert(UseCompressedOops, "currently requested address used only for compressed oops");
     if (PrintCompressedOopsMode) {
       tty->cr();
-      tty->print_cr("Reserved memory at not requested address: " PTR_FORMAT " vs " PTR_FORMAT, base, requested_address);
+      tty->print_cr("Reserved memory not at requested address: " PTR_FORMAT " vs " PTR_FORMAT, base, requested_address);
     }
     // OS ignored requested address. Try different address.
     if (special) {
@@ -162,11 +162,11 @@
   assert(prefix_align != 0, "sanity");
   assert(suffix_size != 0, "sanity");
   assert(suffix_align != 0, "sanity");
-  assert((prefix_size & prefix_align - 1) == 0,
+  assert((prefix_size & (prefix_align - 1)) == 0,
     "prefix_size not divisible by prefix_align");
-  assert((suffix_size & suffix_align - 1) == 0,
+  assert((suffix_size & (suffix_align - 1)) == 0,
     "suffix_size not divisible by suffix_align");
-  assert((suffix_align & prefix_align - 1) == 0,
+  assert((suffix_align & (prefix_align - 1)) == 0,
     "suffix_align not divisible by prefix_align");
 
   // Assert that if noaccess_prefix is used, it is the same as prefix_align.
@@ -210,8 +210,8 @@
   if (addr == NULL) return;
 
   // Check whether the result has the needed alignment (unlikely unless
-  // prefix_align == suffix_align).
-  const size_t ofs = size_t(addr) + adjusted_prefix_size & suffix_align - 1;
+  // prefix_align < suffix_align).
+  const size_t ofs = (size_t(addr) + adjusted_prefix_size) & (suffix_align - 1);
   if (ofs != 0) {
     // Wrong alignment.  Release, allocate more space and do manual alignment.
     //
@@ -232,6 +232,15 @@
       addr = reserve_and_align(size + suffix_align, adjusted_prefix_size,
                                prefix_align, suffix_size, suffix_align);
     }
+
+    if (requested_address != 0 &&
+        failed_to_reserve_as_requested(addr, requested_address, size, false)) {
+      // As a result of the alignment constraints, the allocated addr differs
+      // from the requested address. Return back to the caller who can
+      // take remedial action (like try again without a requested address).
+      assert(_base == NULL, "should be");
+      return;
+    }
   }
 
   _base = addr;
@@ -245,13 +254,19 @@
                                const size_t noaccess_prefix,
                                bool executable) {
   const size_t granularity = os::vm_allocation_granularity();
-  assert((size & granularity - 1) == 0,
+  assert((size & (granularity - 1)) == 0,
          "size not aligned to os::vm_allocation_granularity()");
-  assert((alignment & granularity - 1) == 0,
+  assert((alignment & (granularity - 1)) == 0,
          "alignment not aligned to os::vm_allocation_granularity()");
   assert(alignment == 0 || is_power_of_2((intptr_t)alignment),
          "not a power of 2");
 
+  alignment = MAX2(alignment, (size_t)os::vm_page_size());
+
+  // Assert that if noaccess_prefix is used, it is the same as alignment.
+  assert(noaccess_prefix == 0 ||
+         noaccess_prefix == alignment, "noaccess prefix wrong");
+
   _base = NULL;
   _size = 0;
   _special = false;
@@ -282,10 +297,8 @@
         return;
       }
       // Check alignment constraints
-      if (alignment > 0) {
-        assert((uintptr_t) base % alignment == 0,
-               "Large pages returned a non-aligned address");
-      }
+      assert((uintptr_t) base % alignment == 0,
+             "Large pages returned a non-aligned address");
       _special = true;
     } else {
       // failed; try to reserve regular memory below
@@ -321,7 +334,7 @@
     if (base == NULL) return;
 
     // Check alignment constraints
-    if (alignment > 0 && ((size_t)base & alignment - 1) != 0) {
+    if ((((size_t)base + noaccess_prefix) & (alignment - 1)) != 0) {
       // Base not aligned, retry
       if (!os::release_memory(base, size)) fatal("os::release_memory failed");
       // Reserve size large enough to do manual alignment and
@@ -338,12 +351,21 @@
         os::release_memory(extra_base, extra_size);
         base = os::reserve_memory(size, base);
       } while (base == NULL);
+
+      if (requested_address != 0 &&
+          failed_to_reserve_as_requested(base, requested_address, size, false)) {
+        // As a result of the alignment constraints, the allocated base differs
+        // from the requested address. Return back to the caller who can
+        // take remedial action (like try again without a requested address).
+        assert(_base == NULL, "should be");
+        return;
+      }
     }
   }
   // Done
   _base = base;
   _size = size;
-  _alignment = MAX2(alignment, (size_t) os::vm_page_size());
+  _alignment = alignment;
   _noaccess_prefix = noaccess_prefix;
 
   // Assert that if noaccess_prefix is used, it is the same as alignment.