diff options
Diffstat (limited to 'src/share/vm/gc_implementation/g1/g1HotCardCache.cpp')
| -rw-r--r-- | src/share/vm/gc_implementation/g1/g1HotCardCache.cpp | 99 |
1 files changed, 45 insertions, 54 deletions
diff --git a/src/share/vm/gc_implementation/g1/g1HotCardCache.cpp b/src/share/vm/gc_implementation/g1/g1HotCardCache.cpp index 0c51c318f..f1f807c67 100644 --- a/src/share/vm/gc_implementation/g1/g1HotCardCache.cpp +++ b/src/share/vm/gc_implementation/g1/g1HotCardCache.cpp @@ -1,5 +1,5 @@ /* - * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved. + * Copyright (c) 2013, 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 @@ -36,16 +36,13 @@ void G1HotCardCache::initialize(G1RegionToSpaceMapper* card_counts_storage) { if (default_use_cache()) { _use_cache = true; - _hot_cache_size = (1 << G1ConcRSLogCacheSize); + _hot_cache_size = (size_t)1 << G1ConcRSLogCacheSize; _hot_cache = NEW_C_HEAP_ARRAY(jbyte*, _hot_cache_size, mtGC); - _n_hot = 0; - _hot_cache_idx = 0; + reset_hot_cache_internal(); // For refining the cards in the hot cache in parallel - uint n_workers = (ParallelGCThreads > 0 ? - _g1h->workers()->total_workers() : 1); - _hot_cache_par_chunk_size = MAX2(1, _hot_cache_size / (int)n_workers); + _hot_cache_par_chunk_size = (int)(ParallelGCThreads > 0 ? ClaimChunkSize : _hot_cache_size); _hot_cache_par_claimed_idx = 0; _card_counts.initialize(card_counts_storage); @@ -66,26 +63,21 @@ jbyte* G1HotCardCache::insert(jbyte* card_ptr) { // return it for immediate refining. return card_ptr; } - // Otherwise, the card is hot. - jbyte* res = NULL; - MutexLockerEx x(HotCardCache_lock, Mutex::_no_safepoint_check_flag); - if (_n_hot == _hot_cache_size) { - res = _hot_cache[_hot_cache_idx]; - _n_hot--; - } - - // Now _n_hot < _hot_cache_size, and we can insert at _hot_cache_idx. - _hot_cache[_hot_cache_idx] = card_ptr; - _hot_cache_idx++; - - if (_hot_cache_idx == _hot_cache_size) { - // Wrap around - _hot_cache_idx = 0; - } - _n_hot++; - - return res; + size_t index = Atomic::add_ptr((intptr_t)1, (volatile intptr_t*)&_hot_cache_idx) - 1; + size_t masked_index = index & (_hot_cache_size - 1); + jbyte* current_ptr = _hot_cache[masked_index]; + + // Try to store the new card pointer into the cache. Compare-and-swap to guard + // against the unlikely event of a race resulting in another card pointer to + // have already been written to the cache. In this case we will return + // card_ptr in favor of the other option, which would be starting over. This + // should be OK since card_ptr will likely be the older card already when/if + // this ever happens. + jbyte* previous_ptr = (jbyte*)Atomic::cmpxchg_ptr(card_ptr, + &_hot_cache[masked_index], + current_ptr); + return (previous_ptr == current_ptr) ? previous_ptr : card_ptr; } void G1HotCardCache::drain(uint worker_i, @@ -98,38 +90,37 @@ void G1HotCardCache::drain(uint worker_i, assert(_hot_cache != NULL, "Logic"); assert(!use_cache(), "cache should be disabled"); - int start_idx; - - while ((start_idx = _hot_cache_par_claimed_idx) < _n_hot) { // read once - int end_idx = start_idx + _hot_cache_par_chunk_size; - - if (start_idx == - Atomic::cmpxchg(end_idx, &_hot_cache_par_claimed_idx, start_idx)) { - // The current worker has successfully claimed the chunk [start_idx..end_idx) - end_idx = MIN2(end_idx, _n_hot); - for (int i = start_idx; i < end_idx; i++) { - jbyte* card_ptr = _hot_cache[i]; - if (card_ptr != NULL) { - if (g1rs->refine_card(card_ptr, worker_i, true)) { - // The part of the heap spanned by the card contains references - // that point into the current collection set. - // We need to record the card pointer in the DirtyCardQueueSet - // that we use for such cards. - // - // The only time we care about recording cards that contain - // references that point into the collection set is during - // RSet updating while within an evacuation pause. - // In this case worker_i should be the id of a GC worker thread - assert(SafepointSynchronize::is_at_safepoint(), "Should be at a safepoint"); - assert(worker_i < (ParallelGCThreads == 0 ? 1 : ParallelGCThreads), - err_msg("incorrect worker id: "UINT32_FORMAT, worker_i)); - - into_cset_dcq->enqueue(card_ptr); - } + while (_hot_cache_par_claimed_idx < _hot_cache_size) { + size_t end_idx = Atomic::add_ptr((intptr_t)_hot_cache_par_chunk_size, + (volatile intptr_t*)&_hot_cache_par_claimed_idx); + size_t start_idx = end_idx - _hot_cache_par_chunk_size; + // The current worker has successfully claimed the chunk [start_idx..end_idx) + end_idx = MIN2(end_idx, _hot_cache_size); + for (size_t i = start_idx; i < end_idx; i++) { + jbyte* card_ptr = _hot_cache[i]; + if (card_ptr != NULL) { + if (g1rs->refine_card(card_ptr, worker_i, true)) { + // The part of the heap spanned by the card contains references + // that point into the current collection set. + // We need to record the card pointer in the DirtyCardQueueSet + // that we use for such cards. + // + // The only time we care about recording cards that contain + // references that point into the collection set is during + // RSet updating while within an evacuation pause. + // In this case worker_i should be the id of a GC worker thread + assert(SafepointSynchronize::is_at_safepoint(), "Should be at a safepoint"); + assert(worker_i < ParallelGCThreads, + err_msg("incorrect worker id: %u", worker_i)); + + into_cset_dcq->enqueue(card_ptr); } + } else { + break; } } } + // The existing entries in the hot card cache, which were just refined // above, are discarded prior to re-enabling the cache near the end of the GC. } |