--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/gc/g1/g1AllocRegion.cpp Wed May 13 15:16:06 2015 +0200
@@ -0,0 +1,304 @@
+/*
+ * Copyright (c) 2011, 2015, 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
+ * 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
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "gc/g1/g1AllocRegion.inline.hpp"
+#include "gc/g1/g1CollectedHeap.inline.hpp"
+#include "runtime/orderAccess.inline.hpp"
+
+G1CollectedHeap* G1AllocRegion::_g1h = NULL;
+HeapRegion* G1AllocRegion::_dummy_region = NULL;
+
+void G1AllocRegion::setup(G1CollectedHeap* g1h, HeapRegion* dummy_region) {
+ assert(_dummy_region == NULL, "should be set once");
+ assert(dummy_region != NULL, "pre-condition");
+ assert(dummy_region->free() == 0, "pre-condition");
+
+ // Make sure that any allocation attempt on this region will fail
+ // and will not trigger any asserts.
+ assert(allocate(dummy_region, 1, false) == NULL, "should fail");
+ assert(par_allocate(dummy_region, 1, false) == NULL, "should fail");
+ assert(allocate(dummy_region, 1, true) == NULL, "should fail");
+ assert(par_allocate(dummy_region, 1, true) == NULL, "should fail");
+
+ _g1h = g1h;
+ _dummy_region = dummy_region;
+}
+
+void G1AllocRegion::fill_up_remaining_space(HeapRegion* alloc_region,
+ bool bot_updates) {
+ assert(alloc_region != NULL && alloc_region != _dummy_region,
+ "pre-condition");
+
+ // Other threads might still be trying to allocate using a CAS out
+ // of the region we are trying to retire, as they can do so without
+ // holding the lock. So, we first have to make sure that noone else
+ // can allocate out of it by doing a maximal allocation. Even if our
+ // CAS attempt fails a few times, we'll succeed sooner or later
+ // given that failed CAS attempts mean that the region is getting
+ // closed to being full.
+ size_t free_word_size = alloc_region->free() / HeapWordSize;
+
+ // This is the minimum free chunk we can turn into a dummy
+ // object. If the free space falls below this, then noone can
+ // allocate in this region anyway (all allocation requests will be
+ // of a size larger than this) so we won't have to perform the dummy
+ // allocation.
+ size_t min_word_size_to_fill = CollectedHeap::min_fill_size();
+
+ while (free_word_size >= min_word_size_to_fill) {
+ HeapWord* dummy = par_allocate(alloc_region, free_word_size, bot_updates);
+ if (dummy != NULL) {
+ // If the allocation was successful we should fill in the space.
+ CollectedHeap::fill_with_object(dummy, free_word_size);
+ alloc_region->set_pre_dummy_top(dummy);
+ break;
+ }
+
+ free_word_size = alloc_region->free() / HeapWordSize;
+ // It's also possible that someone else beats us to the
+ // allocation and they fill up the region. In that case, we can
+ // just get out of the loop.
+ }
+ assert(alloc_region->free() / HeapWordSize < min_word_size_to_fill,
+ "post-condition");
+}
+
+void G1AllocRegion::retire(bool fill_up) {
+ assert(_alloc_region != NULL, ar_ext_msg(this, "not initialized properly"));
+
+ trace("retiring");
+ HeapRegion* alloc_region = _alloc_region;
+ if (alloc_region != _dummy_region) {
+ // We never have to check whether the active region is empty or not,
+ // and potentially free it if it is, given that it's guaranteed that
+ // it will never be empty.
+ assert(!alloc_region->is_empty(),
+ ar_ext_msg(this, "the alloc region should never be empty"));
+
+ if (fill_up) {
+ fill_up_remaining_space(alloc_region, _bot_updates);
+ }
+
+ assert(alloc_region->used() >= _used_bytes_before,
+ ar_ext_msg(this, "invariant"));
+ size_t allocated_bytes = alloc_region->used() - _used_bytes_before;
+ retire_region(alloc_region, allocated_bytes);
+ _used_bytes_before = 0;
+ _alloc_region = _dummy_region;
+ }
+ trace("retired");
+}
+
+HeapWord* G1AllocRegion::new_alloc_region_and_allocate(size_t word_size,
+ bool force) {
+ assert(_alloc_region == _dummy_region, ar_ext_msg(this, "pre-condition"));
+ assert(_used_bytes_before == 0, ar_ext_msg(this, "pre-condition"));
+
+ trace("attempting region allocation");
+ HeapRegion* new_alloc_region = allocate_new_region(word_size, force);
+ if (new_alloc_region != NULL) {
+ new_alloc_region->reset_pre_dummy_top();
+ // Need to do this before the allocation
+ _used_bytes_before = new_alloc_region->used();
+ HeapWord* result = allocate(new_alloc_region, word_size, _bot_updates);
+ assert(result != NULL, ar_ext_msg(this, "the allocation should succeeded"));
+
+ OrderAccess::storestore();
+ // Note that we first perform the allocation and then we store the
+ // region in _alloc_region. This is the reason why an active region
+ // can never be empty.
+ update_alloc_region(new_alloc_region);
+ trace("region allocation successful");
+ return result;
+ } else {
+ trace("region allocation failed");
+ return NULL;
+ }
+ ShouldNotReachHere();
+}
+
+void G1AllocRegion::fill_in_ext_msg(ar_ext_msg* msg, const char* message) {
+ msg->append("[%s] %s c: %u b: %s r: "PTR_FORMAT" u: "SIZE_FORMAT,
+ _name, message, _count, BOOL_TO_STR(_bot_updates),
+ p2i(_alloc_region), _used_bytes_before);
+}
+
+void G1AllocRegion::init() {
+ trace("initializing");
+ assert(_alloc_region == NULL && _used_bytes_before == 0,
+ ar_ext_msg(this, "pre-condition"));
+ assert(_dummy_region != NULL, ar_ext_msg(this, "should have been set"));
+ _alloc_region = _dummy_region;
+ _count = 0;
+ trace("initialized");
+}
+
+void G1AllocRegion::set(HeapRegion* alloc_region) {
+ trace("setting");
+ // We explicitly check that the region is not empty to make sure we
+ // maintain the "the alloc region cannot be empty" invariant.
+ assert(alloc_region != NULL && !alloc_region->is_empty(),
+ ar_ext_msg(this, "pre-condition"));
+ assert(_alloc_region == _dummy_region &&
+ _used_bytes_before == 0 && _count == 0,
+ ar_ext_msg(this, "pre-condition"));
+
+ _used_bytes_before = alloc_region->used();
+ _alloc_region = alloc_region;
+ _count += 1;
+ trace("set");
+}
+
+void G1AllocRegion::update_alloc_region(HeapRegion* alloc_region) {
+ trace("update");
+ // We explicitly check that the region is not empty to make sure we
+ // maintain the "the alloc region cannot be empty" invariant.
+ assert(alloc_region != NULL && !alloc_region->is_empty(),
+ ar_ext_msg(this, "pre-condition"));
+
+ _alloc_region = alloc_region;
+ _alloc_region->set_allocation_context(allocation_context());
+ _count += 1;
+ trace("updated");
+}
+
+HeapRegion* G1AllocRegion::release() {
+ trace("releasing");
+ HeapRegion* alloc_region = _alloc_region;
+ retire(false /* fill_up */);
+ assert(_alloc_region == _dummy_region,
+ ar_ext_msg(this, "post-condition of retire()"));
+ _alloc_region = NULL;
+ trace("released");
+ return (alloc_region == _dummy_region) ? NULL : alloc_region;
+}
+
+#if G1_ALLOC_REGION_TRACING
+void G1AllocRegion::trace(const char* str, size_t word_size, HeapWord* result) {
+ // All the calls to trace that set either just the size or the size
+ // and the result are considered part of level 2 tracing and are
+ // skipped during level 1 tracing.
+ if ((word_size == 0 && result == NULL) || (G1_ALLOC_REGION_TRACING > 1)) {
+ const size_t buffer_length = 128;
+ char hr_buffer[buffer_length];
+ char rest_buffer[buffer_length];
+
+ HeapRegion* alloc_region = _alloc_region;
+ if (alloc_region == NULL) {
+ jio_snprintf(hr_buffer, buffer_length, "NULL");
+ } else if (alloc_region == _dummy_region) {
+ jio_snprintf(hr_buffer, buffer_length, "DUMMY");
+ } else {
+ jio_snprintf(hr_buffer, buffer_length,
+ HR_FORMAT, HR_FORMAT_PARAMS(alloc_region));
+ }
+
+ if (G1_ALLOC_REGION_TRACING > 1) {
+ if (result != NULL) {
+ jio_snprintf(rest_buffer, buffer_length, SIZE_FORMAT" "PTR_FORMAT,
+ word_size, result);
+ } else if (word_size != 0) {
+ jio_snprintf(rest_buffer, buffer_length, SIZE_FORMAT, word_size);
+ } else {
+ jio_snprintf(rest_buffer, buffer_length, "");
+ }
+ } else {
+ jio_snprintf(rest_buffer, buffer_length, "");
+ }
+
+ tty->print_cr("[%s] %u %s : %s %s",
+ _name, _count, hr_buffer, str, rest_buffer);
+ }
+}
+#endif // G1_ALLOC_REGION_TRACING
+
+G1AllocRegion::G1AllocRegion(const char* name,
+ bool bot_updates)
+ : _name(name), _bot_updates(bot_updates),
+ _alloc_region(NULL), _count(0), _used_bytes_before(0),
+ _allocation_context(AllocationContext::system()) { }
+
+
+HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
+ bool force) {
+ return _g1h->new_mutator_alloc_region(word_size, force);
+}
+
+void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
+ size_t allocated_bytes) {
+ _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
+}
+
+HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
+ bool force) {
+ assert(!force, "not supported for GC alloc regions");
+ return _g1h->new_gc_alloc_region(word_size, count(), InCSetState::Young);
+}
+
+void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
+ size_t allocated_bytes) {
+ _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, InCSetState::Young);
+}
+
+HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
+ bool force) {
+ assert(!force, "not supported for GC alloc regions");
+ return _g1h->new_gc_alloc_region(word_size, count(), InCSetState::Old);
+}
+
+void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
+ size_t allocated_bytes) {
+ _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, InCSetState::Old);
+}
+
+HeapRegion* OldGCAllocRegion::release() {
+ HeapRegion* cur = get();
+ if (cur != NULL) {
+ // Determine how far we are from the next card boundary. If it is smaller than
+ // the minimum object size we can allocate into, expand into the next card.
+ HeapWord* top = cur->top();
+ HeapWord* aligned_top = (HeapWord*)align_ptr_up(top, G1BlockOffsetSharedArray::N_bytes);
+
+ size_t to_allocate_words = pointer_delta(aligned_top, top, HeapWordSize);
+
+ if (to_allocate_words != 0) {
+ // We are not at a card boundary. Fill up, possibly into the next, taking the
+ // end of the region and the minimum object size into account.
+ to_allocate_words = MIN2(pointer_delta(cur->end(), cur->top(), HeapWordSize),
+ MAX2(to_allocate_words, G1CollectedHeap::min_fill_size()));
+
+ // Skip allocation if there is not enough space to allocate even the smallest
+ // possible object. In this case this region will not be retained, so the
+ // original problem cannot occur.
+ if (to_allocate_words >= G1CollectedHeap::min_fill_size()) {
+ HeapWord* dummy = attempt_allocation(to_allocate_words, true /* bot_updates */);
+ CollectedHeap::fill_with_object(dummy, to_allocate_words);
+ }
+ }
+ }
+ return G1AllocRegion::release();
+}
+
+