aoqi@0: /* aoqi@0: * Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved. aoqi@0: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. aoqi@0: * aoqi@0: * This code is free software; you can redistribute it and/or modify it aoqi@0: * under the terms of the GNU General Public License version 2 only, as aoqi@0: * published by the Free Software Foundation. aoqi@0: * aoqi@0: * This code is distributed in the hope that it will be useful, but WITHOUT aoqi@0: * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or aoqi@0: * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License aoqi@0: * version 2 for more details (a copy is included in the LICENSE file that aoqi@0: * accompanied this code). aoqi@0: * aoqi@0: * You should have received a copy of the GNU General Public License version aoqi@0: * 2 along with this work; if not, write to the Free Software Foundation, aoqi@0: * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. aoqi@0: * aoqi@0: * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA aoqi@0: * or visit www.oracle.com if you need additional information or have any aoqi@0: * questions. aoqi@0: * aoqi@0: */ aoqi@0: aoqi@0: #ifndef SHARE_VM_RUNTIME_SWEEPER_HPP aoqi@0: #define SHARE_VM_RUNTIME_SWEEPER_HPP aoqi@0: aoqi@0: #include "utilities/ticks.hpp" aoqi@0: // An NmethodSweeper is an incremental cleaner for: aoqi@0: // - cleanup inline caches aoqi@0: // - reclamation of nmethods aoqi@0: // Removing nmethods from the code cache includes two operations aoqi@0: // 1) mark active nmethods aoqi@0: // Is done in 'mark_active_nmethods()'. This function is called at a aoqi@0: // safepoint and marks all nmethods that are active on a thread's stack. aoqi@0: // 2) sweep nmethods aoqi@0: // Is done in sweep_code_cache(). This function is the only place in the aoqi@0: // sweeper where memory is reclaimed. Note that sweep_code_cache() is not aoqi@0: // called at a safepoint. However, sweep_code_cache() stops executing if aoqi@0: // another thread requests a safepoint. Consequently, 'mark_active_nmethods()' aoqi@0: // and sweep_code_cache() cannot execute at the same time. aoqi@0: // To reclaim memory, nmethods are first marked as 'not-entrant'. Methods can aoqi@0: // be made not-entrant by (i) the sweeper, (ii) deoptimization, (iii) dependency aoqi@0: // invalidation, and (iv) being replaced be a different method version (tiered aoqi@0: // compilation). Not-entrant nmethod cannot be called by Java threads, but they aoqi@0: // can still be active on the stack. To ensure that active nmethod are not reclaimed, aoqi@0: // we have to wait until the next marking phase has completed. If a not-entrant aoqi@0: // nmethod was NOT marked as active, it can be converted to 'zombie' state. To safely aoqi@0: // remove the nmethod, all inline caches (IC) that point to the the nmethod must be aoqi@0: // cleared. After that, the nmethod can be evicted from the code cache. Each nmethod's aoqi@0: // state change happens during separate sweeps. It may take at least 3 sweeps before an aoqi@0: // nmethod's space is freed. Sweeping is currently done by compiler threads between aoqi@0: // compilations or at least each 5 sec (NmethodSweepCheckInterval) when the code cache aoqi@0: // is full. aoqi@0: aoqi@0: class NMethodSweeper : public AllStatic { aoqi@0: static long _traversals; // Stack scan count, also sweep ID. aoqi@0: static long _total_nof_code_cache_sweeps; // Total number of full sweeps of the code cache aoqi@0: static long _time_counter; // Virtual time used to periodically invoke sweeper aoqi@0: static long _last_sweep; // Value of _time_counter when the last sweep happened aoqi@0: static nmethod* _current; // Current nmethod aoqi@0: static int _seen; // Nof. nmethod we have currently processed in current pass of CodeCache aoqi@0: static int _flushed_count; // Nof. nmethods flushed in current sweep aoqi@0: static int _zombified_count; // Nof. nmethods made zombie in current sweep aoqi@0: static int _marked_for_reclamation_count; // Nof. nmethods marked for reclaim in current sweep aoqi@0: aoqi@0: static volatile int _sweep_fractions_left; // Nof. invocations left until we are completed with this pass aoqi@0: static volatile int _sweep_started; // Flag to control conc sweeper aoqi@0: static volatile bool _should_sweep; // Indicates if we should invoke the sweeper aoqi@0: static volatile int _bytes_changed; // Counts the total nmethod size if the nmethod changed from: aoqi@0: // 1) alive -> not_entrant aoqi@0: // 2) not_entrant -> zombie aoqi@0: // 3) zombie -> marked_for_reclamation aoqi@0: // Stat counters aoqi@0: static long _total_nof_methods_reclaimed; // Accumulated nof methods flushed aoqi@0: static long _total_nof_c2_methods_reclaimed; // Accumulated nof C2-compiled methods flushed aoqi@0: static size_t _total_flushed_size; // Total size of flushed methods aoqi@0: static int _hotness_counter_reset_val; aoqi@0: aoqi@0: static Tickspan _total_time_sweeping; // Accumulated time sweeping aoqi@0: static Tickspan _total_time_this_sweep; // Total time this sweep aoqi@0: static Tickspan _peak_sweep_time; // Peak time for a full sweep aoqi@0: static Tickspan _peak_sweep_fraction_time; // Peak time sweeping one fraction aoqi@0: aoqi@0: static int process_nmethod(nmethod *nm); aoqi@0: static void release_nmethod(nmethod* nm); aoqi@0: aoqi@0: static bool sweep_in_progress(); aoqi@0: static void sweep_code_cache(); aoqi@0: aoqi@0: public: aoqi@0: static long traversal_count() { return _traversals; } aoqi@0: static int total_nof_methods_reclaimed() { return _total_nof_methods_reclaimed; } aoqi@0: static const Tickspan total_time_sweeping() { return _total_time_sweeping; } aoqi@0: static const Tickspan peak_sweep_time() { return _peak_sweep_time; } aoqi@0: static const Tickspan peak_sweep_fraction_time() { return _peak_sweep_fraction_time; } aoqi@0: static void log_sweep(const char* msg, const char* format = NULL, ...) ATTRIBUTE_PRINTF(2, 3); aoqi@0: aoqi@0: aoqi@0: #ifdef ASSERT aoqi@0: static bool is_sweeping(nmethod* which) { return _current == which; } aoqi@0: // Keep track of sweeper activity in the ring buffer aoqi@0: static void record_sweep(nmethod* nm, int line); aoqi@0: static void report_events(int id, address entry); aoqi@0: static void report_events(); aoqi@0: #endif aoqi@0: aoqi@0: static void mark_active_nmethods(); // Invoked at the end of each safepoint aoqi@0: static void possibly_sweep(); // Compiler threads call this to sweep aoqi@0: aoqi@0: static int hotness_counter_reset_val(); aoqi@0: static void report_state_change(nmethod* nm); aoqi@0: static void possibly_enable_sweeper(); aoqi@0: static void print(); // Printing/debugging aoqi@0: }; aoqi@0: aoqi@0: #endif // SHARE_VM_RUNTIME_SWEEPER_HPP