/* * Copyright (c) 2007, 2010, 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 "memory/allocation.inline.hpp" #include "memory/cardTableModRefBS.hpp" #include "memory/cardTableRS.hpp" #include "memory/sharedHeap.hpp" #include "memory/space.inline.hpp" #include "memory/universe.hpp" #include "runtime/java.hpp" #include "runtime/mutexLocker.hpp" #include "runtime/virtualspace.hpp" void CardTableModRefBS::par_non_clean_card_iterate_work(Space* sp, MemRegion mr, DirtyCardToOopClosure* dcto_cl, MemRegionClosure* cl, bool clear, int n_threads) { if (n_threads > 0) { assert((n_threads == 1 && ParallelGCThreads == 0) || n_threads <= (int)ParallelGCThreads, "# worker threads != # requested!"); // Make sure the LNC array is valid for the space. jbyte** lowest_non_clean; uintptr_t lowest_non_clean_base_chunk_index; size_t lowest_non_clean_chunk_size; get_LNC_array_for_space(sp, lowest_non_clean, lowest_non_clean_base_chunk_index, lowest_non_clean_chunk_size); int n_strides = n_threads * StridesPerThread; SequentialSubTasksDone* pst = sp->par_seq_tasks(); pst->set_par_threads(n_threads); pst->set_n_tasks(n_strides); int stride = 0; while (!pst->is_task_claimed(/* reference */ stride)) { process_stride(sp, mr, stride, n_strides, dcto_cl, cl, clear, lowest_non_clean, lowest_non_clean_base_chunk_index, lowest_non_clean_chunk_size); } if (pst->all_tasks_completed()) { // Clear lowest_non_clean array for next time. intptr_t first_chunk_index = addr_to_chunk_index(mr.start()); uintptr_t last_chunk_index = addr_to_chunk_index(mr.last()); for (uintptr_t ch = first_chunk_index; ch <= last_chunk_index; ch++) { intptr_t ind = ch - lowest_non_clean_base_chunk_index; assert(0 <= ind && ind < (intptr_t)lowest_non_clean_chunk_size, "Bounds error"); lowest_non_clean[ind] = NULL; } } } } void CardTableModRefBS:: process_stride(Space* sp, MemRegion used, jint stride, int n_strides, DirtyCardToOopClosure* dcto_cl, MemRegionClosure* cl, bool clear, jbyte** lowest_non_clean, uintptr_t lowest_non_clean_base_chunk_index, size_t lowest_non_clean_chunk_size) { // We don't have to go downwards here; it wouldn't help anyway, // because of parallelism. // Find the first card address of the first chunk in the stride that is // at least "bottom" of the used region. jbyte* start_card = byte_for(used.start()); jbyte* end_card = byte_after(used.last()); uintptr_t start_chunk = addr_to_chunk_index(used.start()); uintptr_t start_chunk_stride_num = start_chunk % n_strides; jbyte* chunk_card_start; if ((uintptr_t)stride >= start_chunk_stride_num) { chunk_card_start = (jbyte*)(start_card + (stride - start_chunk_stride_num) * CardsPerStrideChunk); } else { // Go ahead to the next chunk group boundary, then to the requested stride. chunk_card_start = (jbyte*)(start_card + (n_strides - start_chunk_stride_num + stride) * CardsPerStrideChunk); } while (chunk_card_start < end_card) { // We don't have to go downwards here; it wouldn't help anyway, // because of parallelism. (We take care with "min_done"; see below.) // Invariant: chunk_mr should be fully contained within the "used" region. jbyte* chunk_card_end = chunk_card_start + CardsPerStrideChunk; MemRegion chunk_mr = MemRegion(addr_for(chunk_card_start), chunk_card_end >= end_card ? used.end() : addr_for(chunk_card_end)); assert(chunk_mr.word_size() > 0, "[chunk_card_start > used_end)"); assert(used.contains(chunk_mr), "chunk_mr should be subset of used"); // Process the chunk. process_chunk_boundaries(sp, dcto_cl, chunk_mr, used, lowest_non_clean, lowest_non_clean_base_chunk_index, lowest_non_clean_chunk_size); non_clean_card_iterate_work(chunk_mr, cl, clear); // Find the next chunk of the stride. chunk_card_start += CardsPerStrideChunk * n_strides; } } void CardTableModRefBS:: process_chunk_boundaries(Space* sp, DirtyCardToOopClosure* dcto_cl, MemRegion chunk_mr, MemRegion used, jbyte** lowest_non_clean, uintptr_t lowest_non_clean_base_chunk_index, size_t lowest_non_clean_chunk_size) { // We must worry about the chunk boundaries. // First, set our max_to_do: HeapWord* max_to_do = NULL; uintptr_t cur_chunk_index = addr_to_chunk_index(chunk_mr.start()); cur_chunk_index = cur_chunk_index - lowest_non_clean_base_chunk_index; if (chunk_mr.end() < used.end()) { // This is not the last chunk in the used region. What is the last // object? HeapWord* last_block = sp->block_start(chunk_mr.end()); assert(last_block <= chunk_mr.end(), "In case this property changes."); if (last_block == chunk_mr.end() || !sp->block_is_obj(last_block)) { max_to_do = chunk_mr.end(); } else { // It is an object and starts before the end of the current chunk. // last_obj_card is the card corresponding to the start of the last object // in the chunk. Note that the last object may not start in // the chunk. jbyte* last_obj_card = byte_for(last_block); if (!card_may_have_been_dirty(*last_obj_card)) { // The card containing the head is not dirty. Any marks in // subsequent cards still in this chunk must have been made // precisely; we can cap processing at the end. max_to_do = chunk_mr.end(); } else { // The last object must be considered dirty, and extends onto the // following chunk. Look for a dirty card in that chunk that will // bound our processing. jbyte* limit_card = NULL; size_t last_block_size = sp->block_size(last_block); jbyte* last_card_of_last_obj = byte_for(last_block + last_block_size - 1); jbyte* first_card_of_next_chunk = byte_for(chunk_mr.end()); // This search potentially goes a long distance looking // for the next card that will be scanned. For example, // an object that is an array of primitives will not // have any cards covering regions interior to the array // that will need to be scanned. The scan can be terminated // at the last card of the next chunk. That would leave // limit_card as NULL and would result in "max_to_do" // being set with the LNC value or with the end // of the last block. jbyte* last_card_of_next_chunk = first_card_of_next_chunk + CardsPerStrideChunk; assert(byte_for(chunk_mr.end()) - byte_for(chunk_mr.start()) == CardsPerStrideChunk, "last card of next chunk may be wrong"); jbyte* last_card_to_check = (jbyte*) MIN2(last_card_of_last_obj, last_card_of_next_chunk); for (jbyte* cur = first_card_of_next_chunk; cur <= last_card_to_check; cur++) { if (card_will_be_scanned(*cur)) { limit_card = cur; break; } } assert(0 <= cur_chunk_index+1 && cur_chunk_index+1 < lowest_non_clean_chunk_size, "Bounds error."); // LNC for the next chunk jbyte* lnc_card = lowest_non_clean[cur_chunk_index+1]; if (limit_card == NULL) { limit_card = lnc_card; } if (limit_card != NULL) { if (lnc_card != NULL) { limit_card = (jbyte*)MIN2((intptr_t)limit_card, (intptr_t)lnc_card); } max_to_do = addr_for(limit_card); } else { max_to_do = last_block + last_block_size; } } } assert(max_to_do != NULL, "OOPS!"); } else { max_to_do = used.end(); } // Now we can set the closure we're using so it doesn't to beyond // max_to_do. dcto_cl->set_min_done(max_to_do); #ifndef PRODUCT dcto_cl->set_last_bottom(max_to_do); #endif // Now we set *our" lowest_non_clean entry. // Find the object that spans our boundary, if one exists. // Nothing to do on the first chunk. if (chunk_mr.start() > used.start()) { // first_block is the block possibly spanning the chunk start HeapWord* first_block = sp->block_start(chunk_mr.start()); // Does the block span the start of the chunk and is it // an object? if (first_block < chunk_mr.start() && sp->block_is_obj(first_block)) { jbyte* first_dirty_card = NULL; jbyte* last_card_of_first_obj = byte_for(first_block + sp->block_size(first_block) - 1); jbyte* first_card_of_cur_chunk = byte_for(chunk_mr.start()); jbyte* last_card_of_cur_chunk = byte_for(chunk_mr.last()); jbyte* last_card_to_check = (jbyte*) MIN2((intptr_t) last_card_of_cur_chunk, (intptr_t) last_card_of_first_obj); for (jbyte* cur = first_card_of_cur_chunk; cur <= last_card_to_check; cur++) { if (card_will_be_scanned(*cur)) { first_dirty_card = cur; break; } } if (first_dirty_card != NULL) { assert(0 <= cur_chunk_index && cur_chunk_index < lowest_non_clean_chunk_size, "Bounds error."); lowest_non_clean[cur_chunk_index] = first_dirty_card; } } } } void CardTableModRefBS:: get_LNC_array_for_space(Space* sp, jbyte**& lowest_non_clean, uintptr_t& lowest_non_clean_base_chunk_index, size_t& lowest_non_clean_chunk_size) { int i = find_covering_region_containing(sp->bottom()); MemRegion covered = _covered[i]; size_t n_chunks = chunks_to_cover(covered); // Only the first thread to obtain the lock will resize the // LNC array for the covered region. Any later expansion can't affect // the used_at_save_marks region. // (I observed a bug in which the first thread to execute this would // resize, and then it would cause "expand_and_allocates" that would // Increase the number of chunks in the covered region. Then a second // thread would come and execute this, see that the size didn't match, // and free and allocate again. So the first thread would be using a // freed "_lowest_non_clean" array.) // Do a dirty read here. If we pass the conditional then take the rare // event lock and do the read again in case some other thread had already // succeeded and done the resize. int cur_collection = Universe::heap()->total_collections(); if (_last_LNC_resizing_collection[i] != cur_collection) { MutexLocker x(ParGCRareEvent_lock); if (_last_LNC_resizing_collection[i] != cur_collection) { if (_lowest_non_clean[i] == NULL || n_chunks != _lowest_non_clean_chunk_size[i]) { // Should we delete the old? if (_lowest_non_clean[i] != NULL) { assert(n_chunks != _lowest_non_clean_chunk_size[i], "logical consequence"); FREE_C_HEAP_ARRAY(CardPtr, _lowest_non_clean[i]); _lowest_non_clean[i] = NULL; } // Now allocate a new one if necessary. if (_lowest_non_clean[i] == NULL) { _lowest_non_clean[i] = NEW_C_HEAP_ARRAY(CardPtr, n_chunks); _lowest_non_clean_chunk_size[i] = n_chunks; _lowest_non_clean_base_chunk_index[i] = addr_to_chunk_index(covered.start()); for (int j = 0; j < (int)n_chunks; j++) _lowest_non_clean[i][j] = NULL; } } _last_LNC_resizing_collection[i] = cur_collection; } } // In any case, now do the initialization. lowest_non_clean = _lowest_non_clean[i]; lowest_non_clean_base_chunk_index = _lowest_non_clean_base_chunk_index[i]; lowest_non_clean_chunk_size = _lowest_non_clean_chunk_size[i]; }