diff -r 000000000000 -r f90c822e73f8 src/share/vm/runtime/sweeper.hpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/share/vm/runtime/sweeper.hpp Wed Apr 27 01:25:04 2016 +0800 @@ -0,0 +1,117 @@ +/* + * 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. Sweeping is currently done by compiler threads between +// compilations or at least each 5 sec (NmethodSweepCheckInterval) when the code cache +// is full. + +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 nmethod* _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_fractions_left; // Nof. invocations left until we are completed with this pass + 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 bool sweep_in_progress(); + static void sweep_code_cache(); + + 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 == 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 possibly_sweep(); // Compiler threads call this to sweep + + static int hotness_counter_reset_val(); + static void report_state_change(nmethod* nm); + static void possibly_enable_sweeper(); + static void print(); // Printing/debugging +}; + +#endif // SHARE_VM_RUNTIME_SWEEPER_HPP