diff -r fd16c54261b3 -r 489c9b5090e2 hotspot/src/share/vm/gc_implementation/parNew/parCardTableModRefBS.cpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/hotspot/src/share/vm/gc_implementation/parNew/parCardTableModRefBS.cpp Sat Dec 01 00:00:00 2007 +0000 @@ -0,0 +1,315 @@ +/* + * Copyright (c) 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/_parCardTableModRefBS.cpp.incl" + +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 == (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]; +}