1 /* 2 * Copyright (c) 1997, 2013, 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 #include "utilities/ticks.hpp" 29 // An NmethodSweeper is an incremental cleaner for: 30 // - cleanup inline caches 31 // - reclamation of nmethods 32 // Removing nmethods from the code cache includes two operations 33 // 1) mark active nmethods 34 // Is done in 'mark_active_nmethods()'. This function is called at a 35 // safepoint and marks all nmethods that are active on a thread's stack. 36 // 2) sweep nmethods 37 // Is done in sweep_code_cache(). This function is the only place in the 38 // sweeper where memory is reclaimed. Note that sweep_code_cache() is not 39 // called at a safepoint. However, sweep_code_cache() stops executing if 40 // another thread requests a safepoint. Consequently, 'mark_active_nmethods()' 41 // and sweep_code_cache() cannot execute at the same time. 42 // To reclaim memory, nmethods are first marked as 'not-entrant'. Methods can 43 // be made not-entrant by (i) the sweeper, (ii) deoptimization, (iii) dependency 44 // invalidation, and (iv) being replaced be a different method version (tiered 45 // compilation). Not-entrant nmethod cannot be called by Java threads, but they 46 // can still be active on the stack. To ensure that active nmethod are not reclaimed, 47 // we have to wait until the next marking phase has completed. If a not-entrant 48 // nmethod was NOT marked as active, it can be converted to 'zombie' state. To safely 49 // remove the nmethod, all inline caches (IC) that point to the the nmethod must be 50 // cleared. After that, the nmethod can be evicted from the code cache. Each nmethod's 51 // state change happens during separate sweeps. It may take at least 3 sweeps before an 52 // nmethod's space is freed. Sweeping is currently done by compiler threads between 53 // compilations or at least each 5 sec (NmethodSweepCheckInterval) when the code cache 54 // is full. 55 56 class NMethodSweeper : public AllStatic { 57 static long _traversals; // Stack scan count, also sweep ID. 58 static long _time_counter; // Virtual time used to periodically invoke sweeper 59 static long _last_sweep; // Value of _time_counter when the last sweep happened 60 static nmethod* _current; // Current nmethod 61 static int _seen; // Nof. nmethod we have currently processed in current pass of CodeCache 62 static int _flushed_count; // Nof. nmethods flushed in current sweep 63 static int _zombified_count; // Nof. nmethods made zombie in current sweep 64 static int _marked_for_reclamation_count; // Nof. nmethods marked for reclaim in current sweep 65 66 static volatile int _sweep_fractions_left; // Nof. invocations left until we are completed with this pass 67 static volatile int _sweep_started; // Flag to control conc sweeper 68 static volatile bool _should_sweep; // Indicates if we should invoke the sweeper 69 static volatile int _bytes_changed; // Counts the total nmethod size if the nmethod changed from: 70 // 1) alive -> not_entrant 71 // 2) not_entrant -> zombie 72 // 3) zombie -> marked_for_reclamation 73 // Stat counters 74 static int _total_nof_methods_reclaimed; // Accumulated nof methods flushed 75 static Tickspan _total_time_sweeping; // Accumulated time sweeping 76 static Tickspan _total_time_this_sweep; // Total time this sweep 77 static Tickspan _peak_sweep_time; // Peak time for a full sweep 78 static Tickspan _peak_sweep_fraction_time; // Peak time sweeping one fraction 79 80 static int process_nmethod(nmethod *nm); 81 static void release_nmethod(nmethod* nm); 82 83 static bool sweep_in_progress(); 84 static void sweep_code_cache(); 85 86 static int _hotness_counter_reset_val; 87 88 public: 89 static long traversal_count() { return _traversals; } 90 static int total_nof_methods_reclaimed() { return _total_nof_methods_reclaimed; } 91 static const Tickspan total_time_sweeping() { return _total_time_sweeping; } 92 static const Tickspan peak_sweep_time() { return _peak_sweep_time; } 93 static const Tickspan peak_sweep_fraction_time() { return _peak_sweep_fraction_time; } 94 static void log_sweep(const char* msg, const char* format = NULL, ...); 95 96 97 #ifdef ASSERT 98 static bool is_sweeping(nmethod* which) { return _current == which; } 99 // Keep track of sweeper activity in the ring buffer 100 static void record_sweep(nmethod* nm, int line); 101 static void report_events(int id, address entry); 102 static void report_events(); 103 #endif 104 105 static void mark_active_nmethods(); // Invoked at the end of each safepoint 106 static void possibly_sweep(); // Compiler threads call this to sweep 107 108 static int sort_nmethods_by_hotness(nmethod** nm1, nmethod** nm2); 109 static int hotness_counter_reset_val(); 110 static void report_state_change(nmethod* nm); 111 static void possibly_enable_sweeper(); 112 }; 113 114 #endif // SHARE_VM_RUNTIME_SWEEPER_HPP