diff -r 15e026239a6c -r fcdb8e7ead8f src/hotspot/share/gc/cms/cmsCardTable.cpp --- a/src/hotspot/share/gc/cms/cmsCardTable.cpp Fri Nov 08 14:54:17 2019 +0000 +++ /dev/null Thu Jan 01 00:00:00 1970 +0000 @@ -1,470 +0,0 @@ -/* - * Copyright (c) 2007, 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/cms/cmsCardTable.hpp" -#include "gc/cms/cmsHeap.hpp" -#include "gc/shared/cardTableBarrierSet.hpp" -#include "gc/shared/cardTableRS.hpp" -#include "gc/shared/collectedHeap.hpp" -#include "gc/shared/space.inline.hpp" -#include "memory/allocation.inline.hpp" -#include "memory/virtualspace.hpp" -#include "oops/oop.inline.hpp" -#include "runtime/java.hpp" -#include "runtime/mutexLocker.hpp" -#include "runtime/orderAccess.hpp" -#include "runtime/vmThread.hpp" - -CMSCardTable::CMSCardTable(MemRegion whole_heap) : - CardTableRS(whole_heap, CMSPrecleaningEnabled /* scanned_concurrently */) { -} - -// Returns the number of chunks necessary to cover "mr". -size_t CMSCardTable::chunks_to_cover(MemRegion mr) { - return (size_t)(addr_to_chunk_index(mr.last()) - - addr_to_chunk_index(mr.start()) + 1); -} - -// Returns the index of the chunk in a stride which -// covers the given address. -uintptr_t CMSCardTable::addr_to_chunk_index(const void* addr) { - uintptr_t card = (uintptr_t) byte_for(addr); - return card / ParGCCardsPerStrideChunk; -} - -void CMSCardTable:: -non_clean_card_iterate_parallel_work(Space* sp, MemRegion mr, - OopsInGenClosure* cl, - CardTableRS* ct, - uint n_threads) { - assert(n_threads > 0, "expected n_threads > 0"); - assert(n_threads <= ParallelGCThreads, - "n_threads: %u > ParallelGCThreads: %u", n_threads, ParallelGCThreads); - - // Make sure the LNC array is valid for the space. - CardValue** 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); - - uint n_strides = n_threads * ParGCStridesPerThread; - SequentialSubTasksDone* pst = sp->par_seq_tasks(); - // Sets the condition for completion of the subtask (how many threads - // need to finish in order to be done). - pst->set_n_threads(n_threads); - pst->set_n_tasks(n_strides); - - uint stride = 0; - while (pst->try_claim_task(/* reference */ stride)) { - process_stride(sp, mr, stride, n_strides, - cl, ct, - 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 -CMSCardTable:: -process_stride(Space* sp, - MemRegion used, - jint stride, int n_strides, - OopsInGenClosure* cl, - CardTableRS* ct, - CardValue** lowest_non_clean, - uintptr_t lowest_non_clean_base_chunk_index, - size_t lowest_non_clean_chunk_size) { - // We go from higher to lower addresses here; it wouldn't help that much - // because of the strided parallelism pattern used here. - - // Find the first card address of the first chunk in the stride that is - // at least "bottom" of the used region. - CardValue* start_card = byte_for(used.start()); - CardValue* 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; - CardValue* chunk_card_start; - - if ((uintptr_t)stride >= start_chunk_stride_num) { - chunk_card_start = (start_card + - (stride - start_chunk_stride_num) * ParGCCardsPerStrideChunk); - } else { - // Go ahead to the next chunk group boundary, then to the requested stride. - chunk_card_start = (start_card + - (n_strides - start_chunk_stride_num + stride) * ParGCCardsPerStrideChunk); - } - - while (chunk_card_start < end_card) { - // Even though we go from lower to higher addresses below, the - // strided parallelism can interleave the actual processing of the - // dirty pages in various ways. For a specific chunk within this - // stride, we take care to avoid double scanning or missing a card - // by suitably initializing the "min_done" field in process_chunk_boundaries() - // below, together with the dirty region extension accomplished in - // DirtyCardToOopClosure::do_MemRegion(). - CardValue* chunk_card_end = chunk_card_start + ParGCCardsPerStrideChunk; - // Invariant: chunk_mr should be fully contained within the "used" region. - 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"); - - // This function is used by the parallel card table iteration. - const bool parallel = true; - - DirtyCardToOopClosure* dcto_cl = sp->new_dcto_cl(cl, precision(), - cl->gen_boundary(), - parallel); - ClearNoncleanCardWrapper clear_cl(dcto_cl, ct, parallel); - - - // 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); - - // We want the LNC array updates above in process_chunk_boundaries - // to be visible before any of the card table value changes as a - // result of the dirty card iteration below. - OrderAccess::storestore(); - - // We want to clear the cards: clear_cl here does the work of finding - // contiguous dirty ranges of cards to process and clear. - clear_cl.do_MemRegion(chunk_mr); - - // Find the next chunk of the stride. - chunk_card_start += ParGCCardsPerStrideChunk * n_strides; - } -} - -void -CMSCardTable:: -process_chunk_boundaries(Space* sp, - DirtyCardToOopClosure* dcto_cl, - MemRegion chunk_mr, - MemRegion used, - CardValue** lowest_non_clean, - uintptr_t lowest_non_clean_base_chunk_index, - size_t lowest_non_clean_chunk_size) -{ - // We must worry about non-array objects that cross chunk boundaries, - // because such objects are both precisely and imprecisely marked: - // .. if the head of such an object is dirty, the entire object - // needs to be scanned, under the interpretation that this - // was an imprecise mark - // .. if the head of such an object is not dirty, we can assume - // precise marking and it's efficient to scan just the dirty - // cards. - // In either case, each scanned reference must be scanned precisely - // once so as to avoid cloning of a young referent. For efficiency, - // our closures depend on this property and do not protect against - // double scans. - - uintptr_t start_chunk_index = addr_to_chunk_index(chunk_mr.start()); - assert(start_chunk_index >= lowest_non_clean_base_chunk_index, "Bounds error."); - uintptr_t cur_chunk_index = start_chunk_index - lowest_non_clean_base_chunk_index; - - // First, set "our" lowest_non_clean entry, which would be - // used by the thread scanning an adjoining left chunk with - // a non-array object straddling the mutual boundary. - // Find the object that spans our boundary, if one exists. - // first_block is the block possibly straddling our left boundary. - HeapWord* first_block = sp->block_start(chunk_mr.start()); - assert((chunk_mr.start() != used.start()) || (first_block == chunk_mr.start()), - "First chunk should always have a co-initial block"); - // Does the block straddle the chunk's left boundary, and is it - // a non-array object? - if (first_block < chunk_mr.start() // first block straddles left bdry - && sp->block_is_obj(first_block) // first block is an object - && !(oop(first_block)->is_objArray() // first block is not an array (arrays are precisely dirtied) - || oop(first_block)->is_typeArray())) { - // Find our least non-clean card, so that a left neighbor - // does not scan an object straddling the mutual boundary - // too far to the right, and attempt to scan a portion of - // that object twice. - CardValue* first_dirty_card = NULL; - CardValue* last_card_of_first_obj = - byte_for(first_block + sp->block_size(first_block) - 1); - CardValue* first_card_of_cur_chunk = byte_for(chunk_mr.start()); - CardValue* last_card_of_cur_chunk = byte_for(chunk_mr.last()); - CardValue* last_card_to_check = MIN2(last_card_of_cur_chunk, last_card_of_first_obj); - // Note that this does not need to go beyond our last card - // if our first object completely straddles this chunk. - for (CardValue* cur = first_card_of_cur_chunk; - cur <= last_card_to_check; cur++) { - CardValue val = *cur; - if (card_will_be_scanned(val)) { - first_dirty_card = cur; - break; - } else { - assert(!card_may_have_been_dirty(val), "Error"); - } - } - if (first_dirty_card != NULL) { - assert(cur_chunk_index < lowest_non_clean_chunk_size, "Bounds error."); - assert(lowest_non_clean[cur_chunk_index] == NULL, - "Write exactly once : value should be stable hereafter for this round"); - lowest_non_clean[cur_chunk_index] = first_dirty_card; - } - } else { - // In this case we can help our neighbor by just asking them - // to stop at our first card (even though it may not be dirty). - assert(lowest_non_clean[cur_chunk_index] == NULL, "Write once : value should be stable hereafter"); - CardValue* first_card_of_cur_chunk = byte_for(chunk_mr.start()); - lowest_non_clean[cur_chunk_index] = first_card_of_cur_chunk; - } - - // Next, set our own max_to_do, which will strictly/exclusively bound - // the highest address that we will scan past the right end of our chunk. - HeapWord* max_to_do = NULL; - if (chunk_mr.end() < used.end()) { - // This is not the last chunk in the used region. - // What is our last block? We check the first block of - // the next (right) chunk rather than strictly check our last block - // because it's potentially more efficient to do so. - HeapWord* const 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()) // our last block does not straddle boundary - || !sp->block_is_obj(last_block) // last_block isn't an object - || oop(last_block)->is_objArray() // last_block is an array (precisely marked) - || oop(last_block)->is_typeArray()) { - max_to_do = chunk_mr.end(); - } else { - assert(last_block < chunk_mr.end(), "Tautology"); - // It is a non-array object that straddles the right boundary of this 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. - CardValue* const last_obj_card = byte_for(last_block); - const CardValue val = *last_obj_card; - if (!card_will_be_scanned(val)) { - assert(!card_may_have_been_dirty(val), "Error"); - // The card containing the head is not dirty. Any marks on - // subsequent cards still in this chunk must have been made - // precisely; we can cap processing at the end of our chunk. - 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. - CardValue* limit_card = NULL; - const size_t last_block_size = sp->block_size(last_block); - CardValue* const last_card_of_last_obj = - byte_for(last_block + last_block_size - 1); - CardValue* const 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, terminating - // at the end of the last_block, if no earlier dirty card - // is found. - assert(byte_for(chunk_mr.end()) - byte_for(chunk_mr.start()) == ParGCCardsPerStrideChunk, - "last card of next chunk may be wrong"); - for (CardValue* cur = first_card_of_next_chunk; - cur <= last_card_of_last_obj; cur++) { - const CardValue val = *cur; - if (card_will_be_scanned(val)) { - limit_card = cur; break; - } else { - assert(!card_may_have_been_dirty(val), "Error: card can't be skipped"); - } - } - if (limit_card != NULL) { - max_to_do = addr_for(limit_card); - assert(limit_card != NULL && max_to_do != NULL, "Error"); - } else { - // The following is a pessimistic value, because it's possible - // that a dirty card on a subsequent chunk has been cleared by - // the time we get to look at it; we'll correct for that further below, - // using the LNC array which records the least non-clean card - // before cards were cleared in a particular chunk. - limit_card = last_card_of_last_obj; - max_to_do = last_block + last_block_size; - assert(limit_card != NULL && max_to_do != NULL, "Error"); - } - assert(0 < cur_chunk_index+1 && cur_chunk_index+1 < lowest_non_clean_chunk_size, - "Bounds error."); - // It is possible that a dirty card for the last object may have been - // cleared before we had a chance to examine it. In that case, the value - // will have been logged in the LNC for that chunk. - // We need to examine as many chunks to the right as this object - // covers. However, we need to bound this checking to the largest - // entry in the LNC array: this is because the heap may expand - // after the LNC array has been created but before we reach this point, - // and the last block in our chunk may have been expanded to include - // the expansion delta (and possibly subsequently allocated from, so - // it wouldn't be sufficient to check whether that last block was - // or was not an object at this point). - uintptr_t last_chunk_index_to_check = addr_to_chunk_index(last_block + last_block_size - 1) - - lowest_non_clean_base_chunk_index; - const uintptr_t last_chunk_index = addr_to_chunk_index(used.last()) - - lowest_non_clean_base_chunk_index; - if (last_chunk_index_to_check > last_chunk_index) { - assert(last_block + last_block_size > used.end(), - "Inconsistency detected: last_block [" PTR_FORMAT "," PTR_FORMAT "]" - " does not exceed used.end() = " PTR_FORMAT "," - " yet last_chunk_index_to_check " INTPTR_FORMAT - " exceeds last_chunk_index " INTPTR_FORMAT, - p2i(last_block), p2i(last_block + last_block_size), - p2i(used.end()), - last_chunk_index_to_check, last_chunk_index); - assert(sp->used_region().end() > used.end(), - "Expansion did not happen: " - "[" PTR_FORMAT "," PTR_FORMAT ") -> [" PTR_FORMAT "," PTR_FORMAT ")", - p2i(sp->used_region().start()), p2i(sp->used_region().end()), - p2i(used.start()), p2i(used.end())); - last_chunk_index_to_check = last_chunk_index; - } - for (uintptr_t lnc_index = cur_chunk_index + 1; - lnc_index <= last_chunk_index_to_check; - lnc_index++) { - CardValue* lnc_card = lowest_non_clean[lnc_index]; - if (lnc_card != NULL) { - // we can stop at the first non-NULL entry we find - if (lnc_card <= limit_card) { - limit_card = lnc_card; - max_to_do = addr_for(limit_card); - assert(limit_card != NULL && max_to_do != NULL, "Error"); - } - // In any case, we break now - break; - } // else continue to look for a non-NULL entry if any - } - assert(limit_card != NULL && max_to_do != NULL, "Error"); - } - assert(max_to_do != NULL, "OOPS 1 !"); - } - assert(max_to_do != NULL, "OOPS 2!"); - } else { - max_to_do = used.end(); - } - assert(max_to_do != NULL, "OOPS 3!"); - // 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 -} - -void -CMSCardTable:: -get_LNC_array_for_space(Space* sp, - CardValue**& 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_allocate" 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 = CMSHeap::heap()->total_collections(); - // Updated _last_LNC_resizing_collection[i] must not be visible before - // _lowest_non_clean and friends are visible. Therefore use acquire/release - // to guarantee this on non TSO architecures. - if (OrderAccess::load_acquire(&_last_LNC_resizing_collection[i]) != cur_collection) { - MutexLocker x(ParGCRareEvent_lock); - // This load_acquire is here for clarity only. The MutexLocker already fences. - if (OrderAccess::load_acquire(&_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, mtGC); - _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; - } - } - // Make sure this gets visible only after _lowest_non_clean* was initialized - OrderAccess::release_store(&_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]; -} - -#ifdef ASSERT -void CMSCardTable::verify_used_region_at_save_marks(Space* sp) const { - MemRegion ur = sp->used_region(); - MemRegion urasm = sp->used_region_at_save_marks(); - - if (!ur.contains(urasm)) { - log_warning(gc)("CMS+ParNew: Did you forget to call save_marks()? " - "[" PTR_FORMAT ", " PTR_FORMAT ") is not contained in " - "[" PTR_FORMAT ", " PTR_FORMAT ")", - p2i(urasm.start()), p2i(urasm.end()), p2i(ur.start()), p2i(ur.end())); - MemRegion ur2 = sp->used_region(); - MemRegion urasm2 = sp->used_region_at_save_marks(); - if (!ur.equals(ur2)) { - log_warning(gc)("CMS+ParNew: Flickering used_region()!!"); - } - if (!urasm.equals(urasm2)) { - log_warning(gc)("CMS+ParNew: Flickering used_region_at_save_marks()!!"); - } - ShouldNotReachHere(); - } -} -#endif // ASSERT