gc_implementation/shared/mutableSpace.cpp

/*
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 * 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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#include "precompiled.hpp"
#ifndef SERIALGC
#include "gc_implementation/shared/mutableSpace.hpp"
#include "gc_implementation/shared/spaceDecorator.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/safepoint.hpp"
#include "runtime/thread.hpp"
#endif

MutableSpace::MutableSpace(size_t alignment): ImmutableSpace(), _top(NULL), _alignment(alignment) {
  assert(MutableSpace::alignment() >= 0 &&
         MutableSpace::alignment() % os::vm_page_size() == 0,
         "Space should be aligned");
  _mangler = new MutableSpaceMangler(this);
}

MutableSpace::~MutableSpace() {
  delete _mangler;
}

void MutableSpace::numa_setup_pages(MemRegion mr, bool clear_space) {
  if (!mr.is_empty()) {
    size_t page_size = UseLargePages ? alignment() : os::vm_page_size();
    HeapWord *start = (HeapWord*)round_to((intptr_t) mr.start(), page_size);
    HeapWord *end =  (HeapWord*)round_down((intptr_t) mr.end(), page_size);
    if (end > start) {
      size_t size = pointer_delta(end, start, sizeof(char));
      if (clear_space) {
        // Prefer page reallocation to migration.
        os::free_memory((char*)start, size, page_size);
      }
      os::numa_make_global((char*)start, size);
    }
  }
}

void MutableSpace::pretouch_pages(MemRegion mr) {
  for (volatile char *p = (char*)mr.start(); p < (char*)mr.end(); p += os::vm_page_size()) {
    char t = *p; *p = t;
  }
}

void MutableSpace::initialize(MemRegion mr,
                              bool clear_space,
                              bool mangle_space,
                              bool setup_pages) {

  assert(Universe::on_page_boundary(mr.start()) && Universe::on_page_boundary(mr.end()),
         "invalid space boundaries");

  if (setup_pages && (UseNUMA || AlwaysPreTouch)) {
    // The space may move left and right or expand/shrink.
    // We'd like to enforce the desired page placement.
    MemRegion head, tail;
    if (last_setup_region().is_empty()) {
      // If it's the first initialization don't limit the amount of work.
      head = mr;
      tail = MemRegion(mr.end(), mr.end());
    } else {
      // Is there an intersection with the address space?
      MemRegion intersection = last_setup_region().intersection(mr);
      if (intersection.is_empty()) {
        intersection = MemRegion(mr.end(), mr.end());
      }
      // All the sizes below are in words.
      size_t head_size = 0, tail_size = 0;
      if (mr.start() <= intersection.start()) {
        head_size = pointer_delta(intersection.start(), mr.start());
      }
      if(intersection.end() <= mr.end()) {
        tail_size = pointer_delta(mr.end(), intersection.end());
      }
      // Limit the amount of page manipulation if necessary.
      if (NUMASpaceResizeRate > 0 && !AlwaysPreTouch) {
        const size_t change_size = head_size + tail_size;
        const float setup_rate_words = NUMASpaceResizeRate >> LogBytesPerWord;
        head_size = MIN2((size_t)(setup_rate_words * head_size / change_size),
                         head_size);
        tail_size = MIN2((size_t)(setup_rate_words * tail_size / change_size),
                         tail_size);
      }
      head = MemRegion(intersection.start() - head_size, intersection.start());
      tail = MemRegion(intersection.end(), intersection.end() + tail_size);
    }
    assert(mr.contains(head) && mr.contains(tail), "Sanity");

    if (UseNUMA) {
      numa_setup_pages(head, clear_space);
      numa_setup_pages(tail, clear_space);
    }

    if (AlwaysPreTouch) {
      pretouch_pages(head);
      pretouch_pages(tail);
    }

    // Remember where we stopped so that we can continue later.
    set_last_setup_region(MemRegion(head.start(), tail.end()));
  }

  set_bottom(mr.start());
  set_end(mr.end());

  if (clear_space) {
    clear(mangle_space);
  }
}

void MutableSpace::clear(bool mangle_space) {
  set_top(bottom());
  if (ZapUnusedHeapArea && mangle_space) {
    mangle_unused_area();
  }
}

#ifndef PRODUCT
void MutableSpace::check_mangled_unused_area(HeapWord* limit) {
  mangler()->check_mangled_unused_area(limit);
}

void MutableSpace::check_mangled_unused_area_complete() {
  mangler()->check_mangled_unused_area_complete();
}

// Mangle only the unused space that has not previously
// been mangled and that has not been allocated since being
// mangled.
void MutableSpace::mangle_unused_area() {
  mangler()->mangle_unused_area();
}

void MutableSpace::mangle_unused_area_complete() {
  mangler()->mangle_unused_area_complete();
}

void MutableSpace::mangle_region(MemRegion mr) {
  SpaceMangler::mangle_region(mr);
}

void MutableSpace::set_top_for_allocations(HeapWord* v) {
  mangler()->set_top_for_allocations(v);
}

void MutableSpace::set_top_for_allocations() {
  mangler()->set_top_for_allocations(top());
}
#endif

// This version requires locking. */
HeapWord* MutableSpace::allocate(size_t size) {
  assert(Heap_lock->owned_by_self() ||
         (SafepointSynchronize::is_at_safepoint() &&
          Thread::current()->is_VM_thread()),
         "not locked");
  HeapWord* obj = top();
  if (pointer_delta(end(), obj) >= size) {
    HeapWord* new_top = obj + size;
    set_top(new_top);
    assert(is_object_aligned((intptr_t)obj) && is_object_aligned((intptr_t)new_top),
           "checking alignment");
    return obj;
  } else {
    return NULL;
  }
}

// This version is lock-free.
HeapWord* MutableSpace::cas_allocate(size_t size) {
  do {
    HeapWord* obj = top();
    if (pointer_delta(end(), obj) >= size) {
      HeapWord* new_top = obj + size;
      HeapWord* result = (HeapWord*)Atomic::cmpxchg_ptr(new_top, top_addr(), obj);
      // result can be one of two:
      //  the old top value: the exchange succeeded
      //  otherwise: the new value of the top is returned.
      if (result != obj) {
        continue; // another thread beat us to the allocation, try again
      }
      assert(is_object_aligned((intptr_t)obj) && is_object_aligned((intptr_t)new_top),
             "checking alignment");
      return obj;
    } else {
      return NULL;
    }
  } while (true);
}

// Try to deallocate previous allocation. Returns true upon success.
bool MutableSpace::cas_deallocate(HeapWord *obj, size_t size) {
  HeapWord* expected_top = obj + size;
  return (HeapWord*)Atomic::cmpxchg_ptr(obj, top_addr(), expected_top) == expected_top;
}

void MutableSpace::oop_iterate(OopClosure* cl) {
  HeapWord* obj_addr = bottom();
  HeapWord* t = top();
  // Could call objects iterate, but this is easier.
  while (obj_addr < t) {
    obj_addr += oop(obj_addr)->oop_iterate(cl);
  }
}

void MutableSpace::object_iterate(ObjectClosure* cl) {
  HeapWord* p = bottom();
  while (p < top()) {
    cl->do_object(oop(p));
    p += oop(p)->size();
  }
}

void MutableSpace::print_short() const { print_short_on(tty); }
void MutableSpace::print_short_on( outputStream* st) const {
  st->print(" space " SIZE_FORMAT "K, %d%% used", capacity_in_bytes() / K,
            (int) ((double) used_in_bytes() * 100 / capacity_in_bytes()));
}

void MutableSpace::print() const { print_on(tty); }
void MutableSpace::print_on(outputStream* st) const {
  MutableSpace::print_short_on(st);
  st->print_cr(" [" INTPTR_FORMAT "," INTPTR_FORMAT "," INTPTR_FORMAT ")",
                 bottom(), top(), end());
}

void MutableSpace::verify() {
  HeapWord* p = bottom();
  HeapWord* t = top();
  HeapWord* prev_p = NULL;
  while (p < t) {
    oop(p)->verify();
    prev_p = p;
    p += oop(p)->size();
  }
  guarantee(p == top(), "end of last object must match end of space");
}