Mercurial > jdk8-mips64-public > hotspot / changeset

     1.1 --- a/src/cpu/sparc/vm/vm_version_sparc.cpp	Mon May 03 16:31:07 2010 -0400
     1.2 +++ b/src/cpu/sparc/vm/vm_version_sparc.cpp	Mon May 03 17:23:58 2010 -0400
     1.3 @@ -104,6 +104,12 @@
     1.4      if (FLAG_IS_DEFAULT(OptoLoopAlignment)) {
     1.5        FLAG_SET_DEFAULT(OptoLoopAlignment, 4);
     1.6      }
     1.7 +    // When using CMS, we cannot use memset() in BOT updates because
     1.8 +    // the sun4v/CMT version in libc_psr uses BIS which exposes
     1.9 +    // "phantom zeros" to concurrent readers. See 6948537.
    1.10 +    if (FLAG_IS_DEFAULT(UseMemSetInBOT) && UseConcMarkSweepGC) {
    1.11 +      FLAG_SET_DEFAULT(UseMemSetInBOT, false);
    1.12 +    }
    1.13    }
    1.14  
    1.15    // Use hardware population count instruction if available.

     2.1 --- a/src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.cpp	Mon May 03 16:31:07 2010 -0400
     2.2 +++ b/src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.cpp	Mon May 03 17:23:58 2010 -0400
     2.3 @@ -789,6 +789,14 @@
     2.4    _gc_counters = new CollectorCounters("CMS", 1);
     2.5    _completed_initialization = true;
     2.6    _inter_sweep_timer.start();  // start of time
     2.7 +#ifdef SPARC
     2.8 +  // Issue a stern warning, but allow use for experimentation and debugging.
     2.9 +  if (VM_Version::is_sun4v() && UseMemSetInBOT) {
    2.10 +    assert(!FLAG_IS_DEFAULT(UseMemSetInBOT), "Error");
    2.11 +    warning("Experimental flag -XX:+UseMemSetInBOT is known to cause instability"
    2.12 +            " on sun4v; please understand that you are using at your own risk!");
    2.13 +  }
    2.14 +#endif
    2.15  }
    2.16  
    2.17  const char* ConcurrentMarkSweepGeneration::name() const {

     3.1 --- a/src/share/vm/memory/blockOffsetTable.hpp	Mon May 03 16:31:07 2010 -0400
     3.2 +++ b/src/share/vm/memory/blockOffsetTable.hpp	Mon May 03 17:23:58 2010 -0400
     3.3 @@ -140,14 +140,38 @@
     3.4             "right address out of range");
     3.5      assert(left  < right, "Heap addresses out of order");
     3.6      size_t num_cards = pointer_delta(right, left) >> LogN_words;
     3.7 -    memset(&_offset_array[index_for(left)], offset, num_cards);
     3.8 +
     3.9 +    // Below, we may use an explicit loop instead of memset()
    3.10 +    // because on certain platforms memset() can give concurrent
    3.11 +    // readers "out-of-thin-air," phantom zeros; see 6948537.
    3.12 +    if (UseMemSetInBOT) {
    3.13 +      memset(&_offset_array[index_for(left)], offset, num_cards);
    3.14 +    } else {
    3.15 +      size_t i = index_for(left);
    3.16 +      const size_t end = i + num_cards;
    3.17 +      for (; i < end; i++) {
    3.18 +        _offset_array[i] = offset;
    3.19 +      }
    3.20 +    }
    3.21    }
    3.22  
    3.23    void set_offset_array(size_t left, size_t right, u_char offset) {
    3.24      assert(right < _vs.committed_size(), "right address out of range");
    3.25      assert(left  <= right, "indexes out of order");
    3.26      size_t num_cards = right - left + 1;
    3.27 -    memset(&_offset_array[left], offset, num_cards);
    3.28 +
    3.29 +    // Below, we may use an explicit loop instead of memset
    3.30 +    // because on certain platforms memset() can give concurrent
    3.31 +    // readers "out-of-thin-air," phantom zeros; see 6948537.
    3.32 +    if (UseMemSetInBOT) {
    3.33 +      memset(&_offset_array[left], offset, num_cards);
    3.34 +    } else {
    3.35 +      size_t i = left;
    3.36 +      const size_t end = i + num_cards;
    3.37 +      for (; i < end; i++) {
    3.38 +        _offset_array[i] = offset;
    3.39 +      }
    3.40 +    }
    3.41    }
    3.42  
    3.43    void check_offset_array(size_t index, HeapWord* high, HeapWord* low) const {

     4.1 --- a/src/share/vm/runtime/globals.hpp	Mon May 03 16:31:07 2010 -0400
     4.2 +++ b/src/share/vm/runtime/globals.hpp	Mon May 03 17:23:58 2010 -0400
     4.3 @@ -327,6 +327,10 @@
     4.4    product(bool, UseMembar, false,                                           \
     4.5            "(Unstable) Issues membars on thread state transitions")          \
     4.6                                                                              \
     4.7 +  /* Temporary: See 6948537 */                                             \
     4.8 +  experimental(bool, UseMemSetInBOT, true,                                  \
     4.9 +          "(Unstable) uses memset in BOT updates in GC code")               \
    4.10 +                                                                            \
    4.11    diagnostic(bool, UnlockDiagnosticVMOptions, trueInDebug,                  \
    4.12            "Enable normal processing of flags relating to field diagnostics")\
    4.13                                                                              \