OpenJDK / jdk / jdk
changeset 57721:adcb848a9ecc
8236878: Use atomic instruction to update StringDedupTable's entries and entries_removed counters
Reviewed-by: rkennke, shade
| author | zgu |
|---|---|
| date | Thu, 16 Jan 2020 18:36:24 -0500 |
| parents | 9aba9109a25e |
| children | 5c660d2d97ff |
| files | src/hotspot/share/gc/shared/stringdedup/stringDedupTable.cpp src/hotspot/share/gc/shared/stringdedup/stringDedupTable.hpp |
| diffstat | 2 files changed, 11 insertions(+), 9 deletions(-) [+] |
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--- a/src/hotspot/share/gc/shared/stringdedup/stringDedupTable.cpp Thu Jan 16 08:28:21 2020 -0500 +++ b/src/hotspot/share/gc/shared/stringdedup/stringDedupTable.cpp Thu Jan 16 18:36:24 2020 -0500 @@ -1,5 +1,5 @@ /* - * Copyright (c) 2014, 2019, Oracle and/or its affiliates. All rights reserved. + * Copyright (c) 2014, 2020, 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 @@ -215,7 +215,7 @@ const uintx StringDedupTable::_rehash_threshold = (uintx)(_rehash_multiple * _grow_load_factor); uintx StringDedupTable::_entries_added = 0; -uintx StringDedupTable::_entries_removed = 0; +volatile uintx StringDedupTable::_entries_removed = 0; uintx StringDedupTable::_resize_count = 0; uintx StringDedupTable::_rehash_count = 0; @@ -477,11 +477,13 @@ removed += unlink_or_oops_do(cl, table_half + partition_begin, table_half + partition_end, worker_id); } - // Delayed update to avoid contention on the table lock + // Do atomic update here instead of taking StringDedupTable_lock. This allows concurrent + // cleanup when multiple workers are cleaning up the table, while the mutators are blocked + // on StringDedupTable_lock. if (removed > 0) { - MutexLocker ml(StringDedupTable_lock, Mutex::_no_safepoint_check_flag); - _table->_entries -= removed; - _entries_removed += removed; + assert_locked_or_safepoint_weak(StringDedupTable_lock); + Atomic::sub(&_table->_entries, removed); + Atomic::add(&_entries_removed, removed); } }
--- a/src/hotspot/share/gc/shared/stringdedup/stringDedupTable.hpp Thu Jan 16 08:28:21 2020 -0500 +++ b/src/hotspot/share/gc/shared/stringdedup/stringDedupTable.hpp Thu Jan 16 18:36:24 2020 -0500 @@ -1,5 +1,5 @@ /* - * Copyright (c) 2014, 2019, Oracle and/or its affiliates. All rights reserved. + * Copyright (c) 2014, 2020, 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 @@ -122,7 +122,7 @@ StringDedupEntry** _buckets; size_t _size; - uintx _entries; + volatile uintx _entries; uintx _shrink_threshold; uintx _grow_threshold; bool _rehash_needed; @@ -144,7 +144,7 @@ // Table statistics, only used for logging. static uintx _entries_added; - static uintx _entries_removed; + static volatile uintx _entries_removed; static uintx _resize_count; static uintx _rehash_count;