--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/g1/heterogeneousHeapRegionManager.cpp Fri Dec 21 08:18:59 2018 -0800
@@ -0,0 +1,523 @@
+/*
+ * Copyright (c) 2018, 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/g1CollectedHeap.inline.hpp"
+#include "gc/g1/g1ConcurrentRefine.hpp"
+#include "gc/g1/heapRegion.hpp"
+#include "gc/g1/heapRegionManager.inline.hpp"
+#include "gc/g1/heapRegionSet.inline.hpp"
+#include "gc/g1/heterogeneousHeapRegionManager.hpp"
+#include "memory/allocation.hpp"
+
+
+HeterogeneousHeapRegionManager* HeterogeneousHeapRegionManager::manager() {
+ G1CollectedHeap* g1h = G1CollectedHeap::heap();
+ assert(g1h != NULL, "Uninitialized access to HeterogeneousHeapRegionManager::manager()");
+
+ HeapRegionManager* hrm = g1h->hrm();
+ assert(hrm != NULL, "Uninitialized access to HeterogeneousHeapRegionManager::manager()");
+ return (HeterogeneousHeapRegionManager*)hrm;
+}
+
+void HeterogeneousHeapRegionManager::initialize(G1RegionToSpaceMapper* heap_storage,
+ G1RegionToSpaceMapper* prev_bitmap,
+ G1RegionToSpaceMapper* next_bitmap,
+ G1RegionToSpaceMapper* bot,
+ G1RegionToSpaceMapper* cardtable,
+ G1RegionToSpaceMapper* card_counts) {
+ HeapRegionManager::initialize(heap_storage, prev_bitmap, next_bitmap, bot, cardtable, card_counts);
+
+ // We commit bitmap for all regions during initialization and mark the bitmap space as special.
+ // This allows regions to be un-committed while concurrent-marking threads are accessing the bitmap concurrently.
+ _prev_bitmap_mapper->commit_and_set_special();
+ _next_bitmap_mapper->commit_and_set_special();
+}
+
+// expand_by() is called to grow the heap. We grow into nvdimm now.
+// Dram regions are committed later as needed during mutator region allocation or
+// when young list target length is determined after gc cycle.
+uint HeterogeneousHeapRegionManager::expand_by(uint num_regions, WorkGang* pretouch_workers) {
+ uint num_regions_possible = total_regions_committed() >= max_expandable_length() ? 0 : max_expandable_length() - total_regions_committed();
+ uint num_expanded = expand_nvdimm(MIN2(num_regions, num_regions_possible), pretouch_workers);
+ return num_expanded;
+}
+
+// Expands heap starting from 'start' index. The question is should we expand from one memory (e.g. nvdimm) to another (e.g. dram).
+// Looking at the code, expand_at() is called for humongous allocation where 'start' is in nv-dimm.
+// So we only allocate regions in the same kind of memory as 'start'.
+uint HeterogeneousHeapRegionManager::expand_at(uint start, uint num_regions, WorkGang* pretouch_workers) {
+ if (num_regions == 0) {
+ return 0;
+ }
+ uint target_num_regions = MIN2(num_regions, max_expandable_length() - total_regions_committed());
+ uint end = is_in_nvdimm(start) ? end_index_of_nvdimm() : end_index_of_dram();
+
+ uint num_expanded = expand_in_range(start, end, target_num_regions, pretouch_workers);
+ assert(total_regions_committed() <= max_expandable_length(), "must be");
+ return num_expanded;
+}
+
+// This function ensures that there are 'expected_num_regions' committed regions in dram.
+// If new regions are committed, it un-commits that many regions from nv-dimm.
+// If there are already more regions committed in dram, extra regions are un-committed.
+void HeterogeneousHeapRegionManager::adjust_dram_regions(uint expected_num_regions, WorkGang* pretouch_workers) {
+
+ // Release back the extra regions allocated in evacuation failure scenario.
+ if(_no_borrowed_regions > 0) {
+ _no_borrowed_regions -= shrink_dram(_no_borrowed_regions);
+ _no_borrowed_regions -= shrink_nvdimm(_no_borrowed_regions);
+ }
+
+ if(expected_num_regions > free_list_dram_length()) {
+ // If we are going to expand DRAM, we expand a little more so that we can absorb small variations in Young gen sizing.
+ uint targeted_dram_regions = expected_num_regions * (1 + (double)G1YoungExpansionBufferPercent / 100);
+ uint to_be_made_available = targeted_dram_regions - free_list_dram_length();
+
+#ifdef ASSERT
+ uint total_committed_before = total_regions_committed();
+#endif
+ uint can_be_made_available = shrink_nvdimm(to_be_made_available);
+ uint ret = expand_dram(can_be_made_available, pretouch_workers);
+#ifdef ASSERT
+ assert(ret == can_be_made_available, "should be equal");
+ assert(total_committed_before == total_regions_committed(), "invariant not met");
+#endif
+ } else {
+ uint to_be_released = free_list_dram_length() - expected_num_regions;
+ // if number of extra DRAM regions is small, do not shrink.
+ if (to_be_released < expected_num_regions * G1YoungExpansionBufferPercent / 100) {
+ return;
+ }
+
+#ifdef ASSERT
+ uint total_committed_before = total_regions_committed();
+#endif
+ uint ret = shrink_dram(to_be_released);
+ assert(ret == to_be_released, "Should be able to shrink by given amount");
+ ret = expand_nvdimm(to_be_released, pretouch_workers);
+#ifdef ASSERT
+ assert(ret == to_be_released, "Should be able to expand by given amount");
+ assert(total_committed_before == total_regions_committed(), "invariant not met");
+#endif
+ }
+}
+
+uint HeterogeneousHeapRegionManager::total_regions_committed() const {
+ return num_committed_dram() + num_committed_nvdimm();
+}
+
+uint HeterogeneousHeapRegionManager::num_committed_dram() const {
+ // This class does not keep count of committed regions in dram and nv-dimm.
+ // G1RegionToHeteroSpaceMapper keeps this information.
+ return static_cast<G1RegionToHeteroSpaceMapper*>(_heap_mapper)->num_committed_dram();
+}
+
+uint HeterogeneousHeapRegionManager::num_committed_nvdimm() const {
+ // See comment for num_committed_dram()
+ return static_cast<G1RegionToHeteroSpaceMapper*>(_heap_mapper)->num_committed_nvdimm();
+}
+
+// Return maximum number of regions that heap can expand to.
+uint HeterogeneousHeapRegionManager::max_expandable_length() const {
+ return _max_regions;
+}
+
+uint HeterogeneousHeapRegionManager::find_unavailable_in_range(uint start_idx, uint end_idx, uint* res_idx) const {
+ guarantee(res_idx != NULL, "checking");
+ guarantee(start_idx <= (max_length() + 1), "checking");
+
+ uint num_regions = 0;
+
+ uint cur = start_idx;
+ while (cur <= end_idx && is_available(cur)) {
+ cur++;
+ }
+ if (cur == end_idx + 1) {
+ return num_regions;
+ }
+ *res_idx = cur;
+ while (cur <= end_idx && !is_available(cur)) {
+ cur++;
+ }
+ num_regions = cur - *res_idx;
+
+#ifdef ASSERT
+ for (uint i = *res_idx; i < (*res_idx + num_regions); i++) {
+ assert(!is_available(i), "just checking");
+ }
+ assert(cur == end_idx + 1 || num_regions == 0 || is_available(cur),
+ "The region at the current position %u must be available or at the end", cur);
+#endif
+ return num_regions;
+}
+
+uint HeterogeneousHeapRegionManager::expand_dram(uint num_regions, WorkGang* pretouch_workers) {
+ return expand_in_range(start_index_of_dram(), end_index_of_dram(), num_regions, pretouch_workers);
+}
+
+uint HeterogeneousHeapRegionManager::expand_nvdimm(uint num_regions, WorkGang* pretouch_workers) {
+ return expand_in_range(start_index_of_nvdimm(), end_index_of_nvdimm(), num_regions, pretouch_workers);
+}
+
+// Follows same logic as expand_at() form HeapRegionManager.
+uint HeterogeneousHeapRegionManager::expand_in_range(uint start, uint end, uint num_regions, WorkGang* pretouch_gang) {
+
+ uint so_far = 0;
+ uint chunk_start = 0;
+ uint num_last_found = 0;
+ while (so_far < num_regions &&
+ (num_last_found = find_unavailable_in_range(start, end, &chunk_start)) > 0) {
+ uint to_commit = MIN2(num_regions - so_far, num_last_found);
+ make_regions_available(chunk_start, to_commit, pretouch_gang);
+ so_far += to_commit;
+ start = chunk_start + to_commit + 1;
+ }
+
+ return so_far;
+}
+
+// Shrink in the range of indexes which are reserved for dram.
+uint HeterogeneousHeapRegionManager::shrink_dram(uint num_regions, bool update_free_list) {
+ return shrink_in_range(start_index_of_dram(), end_index_of_dram(), num_regions, update_free_list);
+}
+
+// Shrink in the range of indexes which are reserved for nv-dimm.
+uint HeterogeneousHeapRegionManager::shrink_nvdimm(uint num_regions, bool update_free_list) {
+ return shrink_in_range(start_index_of_nvdimm(), end_index_of_nvdimm(), num_regions, update_free_list);
+}
+
+// Find empty regions in given range, un-commit them and return the count.
+uint HeterogeneousHeapRegionManager::shrink_in_range(uint start, uint end, uint num_regions, bool update_free_list) {
+
+ if (num_regions == 0) {
+ return 0;
+ }
+ uint so_far = 0;
+ uint idx_last_found = 0;
+ uint num_last_found;
+ while (so_far < num_regions &&
+ (num_last_found = find_empty_in_range_reverse(start, end, &idx_last_found)) > 0) {
+ uint to_uncommit = MIN2(num_regions - so_far, num_last_found);
+ if(update_free_list) {
+ _free_list.remove_starting_at(at(idx_last_found + num_last_found - to_uncommit), to_uncommit);
+ }
+ uncommit_regions(idx_last_found + num_last_found - to_uncommit, to_uncommit);
+ so_far += to_uncommit;
+ end = idx_last_found;
+ }
+ return so_far;
+}
+
+uint HeterogeneousHeapRegionManager::find_empty_in_range_reverse(uint start_idx, uint end_idx, uint* res_idx) {
+ guarantee(res_idx != NULL, "checking");
+ guarantee(start_idx < max_length(), "checking");
+ guarantee(end_idx < max_length(), "checking");
+ if(start_idx > end_idx) {
+ return 0;
+ }
+
+ uint num_regions_found = 0;
+
+ jlong cur = end_idx;
+ while (cur >= start_idx && !(is_available(cur) && at(cur)->is_empty())) {
+ cur--;
+ }
+ if (cur == start_idx - 1) {
+ return num_regions_found;
+ }
+ jlong old_cur = cur;
+ // cur indexes the first empty region
+ while (cur >= start_idx && is_available(cur) && at(cur)->is_empty()) {
+ cur--;
+ }
+ *res_idx = cur + 1;
+ num_regions_found = old_cur - cur;
+
+#ifdef ASSERT
+ for (uint i = *res_idx; i < (*res_idx + num_regions_found); i++) {
+ assert(at(i)->is_empty(), "just checking");
+ }
+#endif
+ return num_regions_found;
+}
+
+HeapRegion* HeterogeneousHeapRegionManager::allocate_free_region(HeapRegionType type) {
+
+ // We want to prevent mutators from proceeding when we have borrowed regions from the last collection. This
+ // will force a full collection to remedy the situation.
+ // Free region requests from GC threads can proceed.
+ if(type.is_eden() || type.is_humongous()) {
+ if(has_borrowed_regions()) {
+ return NULL;
+ }
+ }
+
+ // old and humongous regions are allocated from nv-dimm; eden and survivor regions are allocated from dram
+ // assumption: dram regions take higher indexes
+ bool from_nvdimm = (type.is_old() || type.is_humongous()) ? true : false;
+ bool from_head = from_nvdimm;
+ HeapRegion* hr = _free_list.remove_region(from_head);
+
+ if (hr != NULL && ( (from_nvdimm && !is_in_nvdimm(hr->hrm_index())) || (!from_nvdimm && !is_in_dram(hr->hrm_index())) ) ) {
+ _free_list.add_ordered(hr);
+ hr = NULL;
+ }
+
+#ifdef ASSERT
+ uint total_committed_before = total_regions_committed();
+#endif
+
+ if (hr == NULL) {
+ if (!from_nvdimm) {
+ uint ret = shrink_nvdimm(1);
+ if (ret == 1) {
+ ret = expand_dram(1, NULL);
+ assert(ret == 1, "We should be able to commit one region");
+ hr = _free_list.remove_region(from_head);
+ }
+ }
+ else { /*is_old*/
+ uint ret = shrink_dram(1);
+ if (ret == 1) {
+ ret = expand_nvdimm(1, NULL);
+ assert(ret == 1, "We should be able to commit one region");
+ hr = _free_list.remove_region(from_head);
+ }
+ }
+ }
+#ifdef ASSERT
+ assert(total_committed_before == total_regions_committed(), "invariant not met");
+#endif
+
+ // When an old region is requested (which happens during collection pause) and we can't find any empty region
+ // in the set of available regions (which is an evacuation failure scenario), we borrow (or pre-allocate) an unavailable region
+ // from nv-dimm. This region is used to evacuate surviving objects from eden, survivor or old.
+ if(hr == NULL && type.is_old()) {
+ hr = borrow_old_region_for_gc();
+ }
+
+ if (hr != NULL) {
+ assert(hr->next() == NULL, "Single region should not have next");
+ assert(is_available(hr->hrm_index()), "Must be committed");
+ }
+ return hr;
+}
+
+uint HeterogeneousHeapRegionManager::find_contiguous_only_empty(size_t num) {
+ if (has_borrowed_regions()) {
+ return G1_NO_HRM_INDEX;
+ }
+ return find_contiguous(start_index_of_nvdimm(), end_index_of_nvdimm(), num, true);
+}
+
+uint HeterogeneousHeapRegionManager::find_contiguous_empty_or_unavailable(size_t num) {
+ if (has_borrowed_regions()) {
+ return G1_NO_HRM_INDEX;
+ }
+ return find_contiguous(start_index_of_nvdimm(), end_index_of_nvdimm(), num, false);
+}
+
+uint HeterogeneousHeapRegionManager::find_contiguous(size_t start, size_t end, size_t num, bool empty_only) {
+ uint found = 0;
+ size_t length_found = 0;
+ uint cur = (uint)start;
+ uint length_unavailable = 0;
+
+ while (length_found < num && cur <= end) {
+ HeapRegion* hr = _regions.get_by_index(cur);
+ if ((!empty_only && !is_available(cur)) || (is_available(cur) && hr != NULL && hr->is_empty())) {
+ // This region is a potential candidate for allocation into.
+ if (!is_available(cur)) {
+ if(shrink_dram(1) == 1) {
+ uint ret = expand_in_range(cur, cur, 1, NULL);
+ assert(ret == 1, "We should be able to expand at this index");
+ } else {
+ length_unavailable++;
+ }
+ }
+ length_found++;
+ }
+ else {
+ // This region is not a candidate. The next region is the next possible one.
+ found = cur + 1;
+ length_found = 0;
+ }
+ cur++;
+ }
+
+ if (length_found == num) {
+ for (uint i = found; i < (found + num); i++) {
+ HeapRegion* hr = _regions.get_by_index(i);
+ // sanity check
+ guarantee((!empty_only && !is_available(i)) || (is_available(i) && hr != NULL && hr->is_empty()),
+ "Found region sequence starting at " UINT32_FORMAT ", length " SIZE_FORMAT
+ " that is not empty at " UINT32_FORMAT ". Hr is " PTR_FORMAT, found, num, i, p2i(hr));
+ }
+ if (!empty_only && length_unavailable > (max_expandable_length() - total_regions_committed())) {
+ // if 'length_unavailable' number of regions will be made available, we will exceed max regions.
+ return G1_NO_HRM_INDEX;
+ }
+ return found;
+ }
+ else {
+ return G1_NO_HRM_INDEX;
+ }
+}
+
+uint HeterogeneousHeapRegionManager::find_highest_free(bool* expanded) {
+ // Loop downwards from the highest dram region index, looking for an
+ // entry which is either free or not yet committed. If not yet
+ // committed, expand_at that index.
+ uint curr = end_index_of_dram();
+ while (true) {
+ HeapRegion *hr = _regions.get_by_index(curr);
+ if (hr == NULL && !(total_regions_committed() < _max_regions)) {
+ uint res = shrink_nvdimm(1);
+ if (res == 1) {
+ res = expand_in_range(curr, curr, 1, NULL);
+ assert(res == 1, "We should be able to expand since shrink was successful");
+ *expanded = true;
+ return curr;
+ }
+ }
+ else {
+ if (hr->is_free()) {
+ *expanded = false;
+ return curr;
+ }
+ }
+ if (curr == start_index_of_dram()) {
+ return G1_NO_HRM_INDEX;
+ }
+ curr--;
+ }
+}
+
+// We need to override this since region 0 which serves are dummy region in base class may not be available here.
+// This is a corner condition when either number of regions is small. When adaptive sizing is used, initial heap size
+// could be just one region. This region is commited in dram to be used for young generation, leaving region 0 (which is in nvdimm)
+// unavailable.
+HeapRegion* HeterogeneousHeapRegionManager::get_dummy_region() {
+ uint curr = 0;
+
+ while (curr < _regions.length()) {
+ if (is_available(curr)) {
+ return new_heap_region(curr);
+ }
+ curr++;
+ }
+ assert(false, "We should always find a region available for dummy region");
+ return NULL;
+}
+
+// First shrink in dram, then in nv-dimm.
+uint HeterogeneousHeapRegionManager::shrink_by(uint num_regions) {
+ // This call is made at end of full collection. Before making this call the region sets are tore down (tear_down_region_sets()).
+ // So shrink() calls below do not need to remove uncomitted regions from free list.
+ uint ret = shrink_dram(num_regions, false /* update_free_list */);
+ ret += shrink_nvdimm(num_regions - ret, false /* update_free_list */);
+ return ret;
+}
+
+void HeterogeneousHeapRegionManager::verify() {
+ HeapRegionManager::verify();
+}
+
+uint HeterogeneousHeapRegionManager::free_list_dram_length() const {
+ return _free_list.num_of_regions_in_range(start_index_of_dram(), end_index_of_dram());
+}
+
+uint HeterogeneousHeapRegionManager::free_list_nvdimm_length() const {
+ return _free_list.num_of_regions_in_range(start_index_of_nvdimm(), end_index_of_nvdimm());
+}
+
+bool HeterogeneousHeapRegionManager::is_in_nvdimm(uint index) const {
+ return index >= start_index_of_nvdimm() && index <= end_index_of_nvdimm();
+}
+
+bool HeterogeneousHeapRegionManager::is_in_dram(uint index) const {
+ return index >= start_index_of_dram() && index <= end_index_of_dram();
+}
+
+// We have to make sure full collection copies all surviving objects to NV-DIMM.
+// We might not have enough regions in nvdimm_set, so we need to make more regions on NV-DIMM available for full collection.
+// Note: by doing this we are breaking the in-variant that total number of committed regions is equal to current heap size.
+// After full collection ends, we will re-establish this in-variant by freeing DRAM regions.
+void HeterogeneousHeapRegionManager::prepare_for_full_collection_start() {
+ _total_commited_before_full_gc = total_regions_committed() - _no_borrowed_regions;
+ _no_borrowed_regions = 0;
+ expand_nvdimm(num_committed_dram(), NULL);
+ remove_all_free_regions();
+}
+
+// We need to bring back the total committed regions to before full collection start.
+// Unless we are close to OOM, all regular (not pinned) regions in DRAM should be free.
+// We shrink all free regions in DRAM and if needed from NV-DIMM (when there are pinned DRAM regions)
+// If we can't bring back committed regions count to _total_commited_before_full_gc, we keep the extra count in _no_borrowed_regions.
+// When this GC finishes, new regions won't be allocated since has_borrowed_regions() is true. VM will be forced to re-try GC
+// with clear soft references followed by OOM error in worst case.
+void HeterogeneousHeapRegionManager::prepare_for_full_collection_end() {
+ uint shrink_size = total_regions_committed() - _total_commited_before_full_gc;
+ uint so_far = 0;
+ uint idx_last_found = 0;
+ uint num_last_found;
+ uint end = (uint)_regions.length() - 1;
+ while (so_far < shrink_size &&
+ (num_last_found = find_empty_in_range_reverse(0, end, &idx_last_found)) > 0) {
+ uint to_uncommit = MIN2(shrink_size - so_far, num_last_found);
+ uncommit_regions(idx_last_found + num_last_found - to_uncommit, to_uncommit);
+ so_far += to_uncommit;
+ end = idx_last_found;
+ }
+ // See comment above the function.
+ _no_borrowed_regions = shrink_size - so_far;
+}
+
+uint HeterogeneousHeapRegionManager::start_index_of_dram() const { return _max_regions;}
+
+uint HeterogeneousHeapRegionManager::end_index_of_dram() const { return 2*_max_regions - 1; }
+
+uint HeterogeneousHeapRegionManager::start_index_of_nvdimm() const { return 0; }
+
+uint HeterogeneousHeapRegionManager::end_index_of_nvdimm() const { return _max_regions - 1; }
+
+// This function is called when there are no free nv-dimm regions.
+// It borrows a region from the set of unavailable regions in nv-dimm for GC purpose.
+HeapRegion* HeterogeneousHeapRegionManager::borrow_old_region_for_gc() {
+ assert(free_list_nvdimm_length() == 0, "this function should be called only when there are no nv-dimm regions in free list");
+
+ uint ret = expand_nvdimm(1, NULL);
+ if(ret != 1) {
+ return NULL;
+ }
+ HeapRegion* hr = _free_list.remove_region(true /*from_head*/);
+ assert(is_in_nvdimm(hr->hrm_index()), "allocated region should be in nv-dimm");
+ _no_borrowed_regions++;
+ return hr;
+}
+
+bool HeterogeneousHeapRegionManager::has_borrowed_regions() const {
+ return _no_borrowed_regions > 0;
+}