1 /* 2 * Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_RUNTIME_SWEEPER_HPP 26 #define SHARE_RUNTIME_SWEEPER_HPP 27 28 class WhiteBox; 29 30 #include "code/codeCache.hpp" 31 #include "utilities/ticks.hpp" 32 33 class CodeBlobClosure; 34 35 // An NmethodSweeper is an incremental cleaner for: 36 // - cleanup inline caches 37 // - reclamation of nmethods 38 // Removing nmethods from the code cache includes two operations 39 // 1) mark active nmethods 40 // Is done in 'mark_active_nmethods()'. This function is called at a 41 // safepoint and marks all nmethods that are active on a thread's stack. 42 // 2) sweep nmethods 43 // Is done in sweep_code_cache(). This function is the only place in the 44 // sweeper where memory is reclaimed. Note that sweep_code_cache() is not 45 // called at a safepoint. However, sweep_code_cache() stops executing if 46 // another thread requests a safepoint. Consequently, 'mark_active_nmethods()' 47 // and sweep_code_cache() cannot execute at the same time. 48 // To reclaim memory, nmethods are first marked as 'not-entrant'. Methods can 49 // be made not-entrant by (i) the sweeper, (ii) deoptimization, (iii) dependency 50 // invalidation, and (iv) being replaced by a different method version (tiered 51 // compilation). Not-entrant nmethods cannot be called by Java threads, but they 52 // can still be active on the stack. To ensure that active nmethods are not reclaimed, 53 // we have to wait until the next marking phase has completed. If a not-entrant 54 // nmethod was NOT marked as active, it can be converted to 'zombie' state. To safely 55 // remove the nmethod, all inline caches (IC) that point to the nmethod must be 56 // cleared. After that, the nmethod can be evicted from the code cache. Each nmethod's 57 // state change happens during separate sweeps. It may take at least 3 sweeps before an 58 // nmethod's space is freed. 59 60 class NMethodSweeper : public AllStatic { 61 private: 62 enum MethodStateChange { 63 None, 64 MadeZombie, 65 Flushed 66 }; 67 static long _traversals; // Stack scan count, also sweep ID. 68 static long _total_nof_code_cache_sweeps; // Total number of full sweeps of the code cache 69 static CompiledMethodIterator _current; // Current compiled method 70 static int _seen; // Nof. nmethod we have currently processed in current pass of CodeCache 71 static size_t _sweep_threshold_bytes; // The threshold for when to invoke sweeps 72 73 static volatile bool _should_sweep; // Indicates if a normal sweep will be done 74 static volatile bool _force_sweep; // Indicates if a forced sweep will be done 75 static volatile size_t _bytes_changed; // Counts the total nmethod size if the nmethod changed from: 76 // 1) alive -> not_entrant 77 // 2) not_entrant -> zombie 78 // Stat counters 79 static long _total_nof_methods_reclaimed; // Accumulated nof methods flushed 80 static long _total_nof_c2_methods_reclaimed; // Accumulated nof C2-compiled methods flushed 81 static size_t _total_flushed_size; // Total size of flushed methods 82 static int _hotness_counter_reset_val; 83 84 static Tickspan _total_time_sweeping; // Accumulated time sweeping 85 static Tickspan _total_time_this_sweep; // Total time this sweep 86 static Tickspan _peak_sweep_time; // Peak time for a full sweep 87 static Tickspan _peak_sweep_fraction_time; // Peak time sweeping one fraction 88 89 static MethodStateChange process_compiled_method(CompiledMethod *nm); 90 91 static void init_sweeper_log() NOT_DEBUG_RETURN; 92 static bool wait_for_stack_scanning(); 93 static void sweep_code_cache(); 94 static void handle_safepoint_request(); 95 static void do_stack_scanning(); 96 static void sweep(); 97 public: traversal_count()98 static long traversal_count() { return _traversals; } sweep_threshold_bytes()99 static size_t sweep_threshold_bytes() { return _sweep_threshold_bytes; } set_sweep_threshold_bytes(size_t threshold)100 static void set_sweep_threshold_bytes(size_t threshold) { _sweep_threshold_bytes = threshold; } total_nof_methods_reclaimed()101 static int total_nof_methods_reclaimed() { return _total_nof_methods_reclaimed; } total_time_sweeping()102 static const Tickspan total_time_sweeping() { return _total_time_sweeping; } peak_sweep_time()103 static const Tickspan peak_sweep_time() { return _peak_sweep_time; } peak_sweep_fraction_time()104 static const Tickspan peak_sweep_fraction_time() { return _peak_sweep_fraction_time; } 105 static void log_sweep(const char* msg, const char* format = NULL, ...) ATTRIBUTE_PRINTF(2, 3); 106 107 #ifdef ASSERT 108 // Keep track of sweeper activity in the ring buffer 109 static void record_sweep(CompiledMethod* nm, int line); 110 #endif 111 112 static CodeBlobClosure* prepare_mark_active_nmethods(); 113 static CodeBlobClosure* prepare_reset_hotness_counters(); 114 115 static void sweeper_loop(); 116 static bool should_start_aggressive_sweep(int code_blob_type); 117 static void force_sweep(); 118 static int hotness_counter_reset_val(); 119 static void report_state_change(nmethod* nm); 120 static void report_allocation(int code_blob_type); // Possibly start the sweeper thread. 121 static void possibly_flush(nmethod* nm); 122 static void print(outputStream* out); // Printing/debugging print()123 static void print() { print(tty); } 124 }; 125 126 #endif // SHARE_RUNTIME_SWEEPER_HPP 127