6711316: Open source the Garbage-First garbage collector

First mercurial integration of the code for the Garbage-First garbage collector.

Reviewed-by: apetrusenko, iveresov, jmasa, sgoldman, tonyp, ysr

hotspot/src/share/vm/gc_implementation/g1/heapRegionSeq.cpp

@@ -0,0 +1,344 @@
+/*
+ * Copyright 2001-2007 Sun Microsystems, Inc.  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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+#include "incls/_precompiled.incl"
+#include "incls/_heapRegionSeq.cpp.incl"
+
+// Local to this file.
+
+static int orderRegions(HeapRegion** hr1p, HeapRegion** hr2p) {
+  if ((*hr1p)->end() <= (*hr2p)->bottom()) return -1;
+  else if ((*hr2p)->end() <= (*hr1p)->bottom()) return 1;
+  else if (*hr1p == *hr2p) return 0;
+  else {
+    assert(false, "We should never compare distinct overlapping regions.");
+  }
+  return 0;
+}
+
+HeapRegionSeq::HeapRegionSeq() :
+  _alloc_search_start(0),
+  // The line below is the worst bit of C++ hackery I've ever written
+  // (Detlefs, 11/23).  You should think of it as equivalent to
+  // "_regions(100, true)": initialize the growable array and inform it
+  // that it should allocate its elem array(s) on the C heap.  The first
+  // argument, however, is actually a comma expression (new-expr, 100).
+  // The purpose of the new_expr is to inform the growable array that it
+  // is *already* allocated on the C heap: it uses the placement syntax to
+  // keep it from actually doing any allocation.
+  _regions((ResourceObj::operator new (sizeof(GrowableArray<HeapRegion*>),
+                                       (void*)&_regions,
+                                       ResourceObj::C_HEAP),
+            100),
+           true),
+  _next_rr_candidate(0),
+  _seq_bottom(NULL)
+{}
+
+// Private methods.
+
+HeapWord*
+HeapRegionSeq::alloc_obj_from_region_index(int ind, size_t word_size) {
+  assert(G1CollectedHeap::isHumongous(word_size),
+         "Allocation size should be humongous");
+  int cur = ind;
+  int first = cur;
+  size_t sumSizes = 0;
+  while (cur < _regions.length() && sumSizes < word_size) {
+    // Loop invariant:
+    //  For all i in [first, cur):
+    //       _regions.at(i)->is_empty()
+    //    && _regions.at(i) is contiguous with its predecessor, if any
+    //  && sumSizes is the sum of the sizes of the regions in the interval
+    //       [first, cur)
+    HeapRegion* curhr = _regions.at(cur);
+    if (curhr->is_empty()
+        && !curhr->is_reserved()
+        && (first == cur
+            || (_regions.at(cur-1)->end() ==
+                curhr->bottom()))) {
+      sumSizes += curhr->capacity() / HeapWordSize;
+    } else {
+      first = cur + 1;
+      sumSizes = 0;
+    }
+    cur++;
+  }
+  if (sumSizes >= word_size) {
+    _alloc_search_start = cur;
+    // Mark the allocated regions as allocated.
+    bool zf = G1CollectedHeap::heap()->allocs_are_zero_filled();
+    HeapRegion* first_hr = _regions.at(first);
+    for (int i = first; i < cur; i++) {
+      HeapRegion* hr = _regions.at(i);
+      if (zf)
+        hr->ensure_zero_filled();
+      {
+        MutexLockerEx x(ZF_mon, Mutex::_no_safepoint_check_flag);
+        hr->set_zero_fill_allocated();
+      }
+      size_t sz = hr->capacity() / HeapWordSize;
+      HeapWord* tmp = hr->allocate(sz);
+      assert(tmp != NULL, "Humongous allocation failure");
+      MemRegion mr = MemRegion(tmp, sz);
+      SharedHeap::fill_region_with_object(mr);
+      hr->declare_filled_region_to_BOT(mr);
+      if (i == first) {
+        first_hr->set_startsHumongous();
+      } else {
+        assert(i > first, "sanity");
+        hr->set_continuesHumongous(first_hr);
+      }
+    }
+    HeapWord* first_hr_bot = first_hr->bottom();
+    HeapWord* obj_end = first_hr_bot + word_size;
+    first_hr->set_top(obj_end);
+    return first_hr_bot;
+  } else {
+    // If we started from the beginning, we want to know why we can't alloc.
+    return NULL;
+  }
+}
+
+void HeapRegionSeq::print_empty_runs(bool reserved_are_empty) {
+  int empty_run = 0;
+  int n_empty = 0;
+  bool at_least_one_reserved = false;
+  int empty_run_start;
+  for (int i = 0; i < _regions.length(); i++) {
+    HeapRegion* r = _regions.at(i);
+    if (r->continuesHumongous()) continue;
+    if (r->is_empty() && (reserved_are_empty || !r->is_reserved())) {
+      assert(!r->isHumongous(), "H regions should not be empty.");
+      if (empty_run == 0) empty_run_start = i;
+      empty_run++;
+      n_empty++;
+      if (r->is_reserved()) {
+        at_least_one_reserved = true;
+      }
+    } else {
+      if (empty_run > 0) {
+        gclog_or_tty->print("  %d:%d", empty_run_start, empty_run);
+        if (reserved_are_empty && at_least_one_reserved)
+          gclog_or_tty->print("(R)");
+        empty_run = 0;
+        at_least_one_reserved = false;
+      }
+    }
+  }
+  if (empty_run > 0) {
+    gclog_or_tty->print(" %d:%d", empty_run_start, empty_run);
+    if (reserved_are_empty && at_least_one_reserved) gclog_or_tty->print("(R)");
+  }
+  gclog_or_tty->print_cr(" [tot = %d]", n_empty);
+}
+
+int HeapRegionSeq::find(HeapRegion* hr) {
+  // FIXME: optimized for adjacent regions of fixed size.
+  int ind = hr->hrs_index();
+  if (ind != -1) {
+    assert(_regions.at(ind) == hr, "Mismatch");
+  }
+  return ind;
+}
+
+
+// Public methods.
+
+void HeapRegionSeq::insert(HeapRegion* hr) {
+  if (_regions.length() == 0
+      || _regions.top()->end() <= hr->bottom()) {
+    hr->set_hrs_index(_regions.length());
+    _regions.append(hr);
+  } else {
+    _regions.append(hr);
+    _regions.sort(orderRegions);
+    for (int i = 0; i < _regions.length(); i++) {
+      _regions.at(i)->set_hrs_index(i);
+    }
+  }
+  char* bot = (char*)_regions.at(0)->bottom();
+  if (_seq_bottom == NULL || bot < _seq_bottom) _seq_bottom = bot;
+}
+
+size_t HeapRegionSeq::length() {
+  return _regions.length();
+}
+
+size_t HeapRegionSeq::free_suffix() {
+  size_t res = 0;
+  int first = _regions.length() - 1;
+  int cur = first;
+  while (cur >= 0 &&
+         (_regions.at(cur)->is_empty()
+          && !_regions.at(cur)->is_reserved()
+          && (first == cur
+              || (_regions.at(cur+1)->bottom() ==
+                  _regions.at(cur)->end())))) {
+      res++;
+      cur--;
+  }
+  return res;
+}
+
+HeapWord* HeapRegionSeq::obj_allocate(size_t word_size) {
+  int cur = _alloc_search_start;
+  // Make sure "cur" is a valid index.
+  assert(cur >= 0, "Invariant.");
+  HeapWord* res = alloc_obj_from_region_index(cur, word_size);
+  if (res == NULL)
+    res = alloc_obj_from_region_index(0, word_size);
+  return res;
+}
+
+void HeapRegionSeq::iterate(HeapRegionClosure* blk) {
+  iterate_from((HeapRegion*)NULL, blk);
+}
+
+// The first argument r is the heap region at which iteration begins.
+// This operation runs fastest when r is NULL, or the heap region for
+// which a HeapRegionClosure most recently returned true, or the
+// heap region immediately to its right in the sequence.  In all
+// other cases a linear search is required to find the index of r.
+
+void HeapRegionSeq::iterate_from(HeapRegion* r, HeapRegionClosure* blk) {
+
+  // :::: FIXME ::::
+  // Static cache value is bad, especially when we start doing parallel
+  // remembered set update. For now just don't cache anything (the
+  // code in the def'd out blocks).
+
+#if 0
+  static int cached_j = 0;
+#endif
+  int len = _regions.length();
+  int j = 0;
+  // Find the index of r.
+  if (r != NULL) {
+#if 0
+    assert(cached_j >= 0, "Invariant.");
+    if ((cached_j < len) && (r == _regions.at(cached_j))) {
+      j = cached_j;
+    } else if ((cached_j + 1 < len) && (r == _regions.at(cached_j + 1))) {
+      j = cached_j + 1;
+    } else {
+      j = find(r);
+#endif
+      if (j < 0) {
+        j = 0;
+      }
+#if 0
+    }
+#endif
+  }
+  int i;
+  for (i = j; i < len; i += 1) {
+    int res = blk->doHeapRegion(_regions.at(i));
+    if (res) {
+#if 0
+      cached_j = i;
+#endif
+      blk->incomplete();
+      return;
+    }
+  }
+  for (i = 0; i < j; i += 1) {
+    int res = blk->doHeapRegion(_regions.at(i));
+    if (res) {
+#if 0
+      cached_j = i;
+#endif
+      blk->incomplete();
+      return;
+    }
+  }
+}
+
+void HeapRegionSeq::iterate_from(int idx, HeapRegionClosure* blk) {
+  int len = _regions.length();
+  int i;
+  for (i = idx; i < len; i++) {
+    if (blk->doHeapRegion(_regions.at(i))) {
+      blk->incomplete();
+      return;
+    }
+  }
+  for (i = 0; i < idx; i++) {
+    if (blk->doHeapRegion(_regions.at(i))) {
+      blk->incomplete();
+      return;
+    }
+  }
+}
+
+MemRegion HeapRegionSeq::shrink_by(size_t shrink_bytes,
+                                   size_t& num_regions_deleted) {
+  assert(shrink_bytes % os::vm_page_size() == 0, "unaligned");
+  assert(shrink_bytes % HeapRegion::GrainBytes == 0, "unaligned");
+
+  if (_regions.length() == 0) {
+    num_regions_deleted = 0;
+    return MemRegion();
+  }
+  int j = _regions.length() - 1;
+  HeapWord* end = _regions.at(j)->end();
+  HeapWord* last_start = end;
+  while (j >= 0 && shrink_bytes > 0) {
+    HeapRegion* cur = _regions.at(j);
+    // We have to leave humongous regions where they are,
+    // and work around them.
+    if (cur->isHumongous()) {
+      return MemRegion(last_start, end);
+    }
+    cur->reset_zero_fill();
+    assert(cur == _regions.top(), "Should be top");
+    if (!cur->is_empty()) break;
+    shrink_bytes -= cur->capacity();
+    num_regions_deleted++;
+    _regions.pop();
+    last_start = cur->bottom();
+    // We need to delete these somehow, but can't currently do so here: if
+    // we do, the ZF thread may still access the deleted region.  We'll
+    // leave this here as a reminder that we have to do something about
+    // this.
+    // delete cur;
+    j--;
+  }
+  return MemRegion(last_start, end);
+}
+
+
+class PrintHeapRegionClosure : public  HeapRegionClosure {
+public:
+  bool doHeapRegion(HeapRegion* r) {
+    gclog_or_tty->print(PTR_FORMAT ":", r);
+    r->print();
+    return false;
+  }
+};
+
+void HeapRegionSeq::print() {
+  PrintHeapRegionClosure cl;
+  iterate(&cl);
+}