sweeper.hpp (original) (raw)

1 /* 2 * Copyright (c) 1997, 2014, 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_VM_RUNTIME_SWEEPER_HPP 26 #define SHARE_VM_RUNTIME_SWEEPER_HPP 27 28 class WhiteBox; 29 30 #include "utilities/ticks.hpp" 31 // An NmethodSweeper is an incremental cleaner for: 32 // - cleanup inline caches 33 // - reclamation of nmethods 34 // Removing nmethods from the code cache includes two operations 35 // 1) mark active nmethods 36 // Is done in 'mark_active_nmethods()'. This function is called at a 37 // safepoint and marks all nmethods that are active on a thread's stack. 38 // 2) sweep nmethods 39 // Is done in sweep_code_cache(). This function is the only place in the 40 // sweeper where memory is reclaimed. Note that sweep_code_cache() is not 41 // called at a safepoint. However, sweep_code_cache() stops executing if 42 // another thread requests a safepoint. Consequently, 'mark_active_nmethods()' 43 // and sweep_code_cache() cannot execute at the same time. 44 // To reclaim memory, nmethods are first marked as 'not-entrant'. Methods can 45 // be made not-entrant by (i) the sweeper, (ii) deoptimization, (iii) dependency 46 // invalidation, and (iv) being replaced be a different method version (tiered 47 // compilation). Not-entrant nmethod cannot be called by Java threads, but they 48 // can still be active on the stack. To ensure that active nmethod are not reclaimed, 49 // we have to wait until the next marking phase has completed. If a not-entrant 50 // nmethod was NOT marked as active, it can be converted to 'zombie' state. To safely 51 // remove the nmethod, all inline caches (IC) that point to the the nmethod must be 52 // cleared. After that, the nmethod can be evicted from the code cache. Each nmethod's 53 // state change happens during separate sweeps. It may take at least 3 sweeps before an 54 // nmethod's space is freed. 55 56 class NMethodSweeper : public AllStatic { 57 private: 58 enum MethodStateChange { 59 None, 60 MadeZombie, 61 MarkedForReclamation, 62 Flushed 63 }; 64 static long _traversals; // Stack scan count, also sweep ID. 65 static long _total_nof_code_cache_sweeps; // Total number of full sweeps of the code cache 66 static long _time_counter; // Virtual time used to periodically invoke sweeper 67 static long _last_sweep; // Value of _time_counter when the last sweep happened 68 static NMethodIterator _current; // Current nmethod 69 static int _seen; // Nof. nmethod we have currently processed in current pass of CodeCache 70 71 static volatile int _sweep_started; // Flag to control conc sweeper 72 static volatile bool _should_sweep; // Indicates if we should invoke the sweeper 73 static volatile bool _force_sweep; // Indicates if we should force a sweep 74 static volatile int _bytes_changed; // Counts the total nmethod size if the nmethod changed from: 75 // 1) alive -> not_entrant 76 // 2) not_entrant -> zombie 77 // 3) zombie -> marked_for_reclamation 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 Monitor _stat_lock; 90 91 static MethodStateChange process_nmethod(nmethod nm); 92 static void release_nmethod(nmethod nm); 93 94 static void init_sweeper_log() NOT_DEBUG_RETURN; 95 static bool wait_for_stack_scanning(); 96 static void sweep_code_cache(); 97 static void handle_safepoint_request(); 98 static void do_stack_scanning(); 99 static void possibly_sweep(); 100 public: 101 static long traversal_count() { return _traversals; } 102 static int total_nof_methods_reclaimed() { return _total_nof_methods_reclaimed; } 103 static const Tickspan total_time_sweeping() { return _total_time_sweeping; } 104 static const Tickspan peak_sweep_time() { return _peak_sweep_time; } 105 static const Tickspan peak_sweep_fraction_time() { return _peak_sweep_fraction_time; } 106 static void log_sweep(const char* msg, const char* format = NULL, ...) ATTRIBUTE_PRINTF(2, 3); 107 108 109 #ifdef ASSERT 110 static bool is_sweeping(nmethod* which) { return _current.method() == which; } 111 // Keep track of sweeper activity in the ring buffer 112 static void record_sweep(nmethod* nm, int line); 113 static void report_events(int id, address entry); 114 static void report_events(); 115 #endif 116 117 static void mark_active_nmethods(); // Invoked at the end of each safepoint 118 static void sweeper_loop(); 119 static void notify(int code_blob_type); // Possibly start the sweeper thread. 120 static void force_sweep(); 121 122 static int hotness_counter_reset_val(); 123 static void report_state_change(nmethod* nm); 124 static void possibly_enable_sweeper(); 125 static void possibly_flush(nmethod* nm); 126 static void print(); // Printing/debugging 127 }; 128 129 #endif // SHARE_VM_RUNTIME_SWEEPER_HPP