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