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.
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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
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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 friend class WhiteBox;
58 private:
59 static long _traversals; // Stack scan count, also sweep ID.
60 static long _total_nof_code_cache_sweeps; // Total number of full sweeps of the code cache
61 static long _time_counter; // Virtual time used to periodically invoke sweeper
62 static long _last_sweep; // Value of _time_counter when the last sweep happened
63 static NMethodIterator _current; // Current nmethod
64 static int _seen; // Nof. nmethod we have currently processed in current pass of CodeCache
65 static int _flushed_count; // Nof. nmethods flushed in current sweep
66 static int _zombified_count; // Nof. nmethods made zombie in current sweep
67 static int _marked_for_reclamation_count; // Nof. nmethods marked for reclaim in current sweep
68
69 static volatile int _sweep_started; // Flag to control conc sweeper
70 static volatile bool _should_sweep; // Indicates if we should invoke the sweeper
71 static volatile int _bytes_changed; // Counts the total nmethod size if the nmethod changed from:
72 // 1) alive -> not_entrant
73 // 2) not_entrant -> zombie
74 // 3) zombie -> marked_for_reclamation
75 // Stat counters
76 static long _total_nof_methods_reclaimed; // Accumulated nof methods flushed
77 static long _total_nof_c2_methods_reclaimed; // Accumulated nof C2-compiled methods flushed
78 static size_t _total_flushed_size; // Total size of flushed methods
79 static int _hotness_counter_reset_val;
80
81 static Tickspan _total_time_sweeping; // Accumulated time sweeping
82 static Tickspan _total_time_this_sweep; // Total time this sweep
83 static Tickspan _peak_sweep_time; // Peak time for a full sweep
84 static Tickspan _peak_sweep_fraction_time; // Peak time sweeping one fraction
85
86 static int process_nmethod(nmethod *nm);
87 static void release_nmethod(nmethod* nm);
88
89 static void init_sweeper_log() NOT_DEBUG_RETURN;
90 static bool wait_for_stack_scanning();
91 static void sweep_code_cache();
92 static void handle_safepoint_request();
93 static void do_stack_scanning();
94 static void possibly_sweep();
95 public:
96 static long traversal_count() { return _traversals; }
97 static int total_nof_methods_reclaimed() { return _total_nof_methods_reclaimed; }
98 static const Tickspan total_time_sweeping() { return _total_time_sweeping; }
99 static const Tickspan peak_sweep_time() { return _peak_sweep_time; }
100 static const Tickspan peak_sweep_fraction_time() { return _peak_sweep_fraction_time; }
101 static void log_sweep(const char* msg, const char* format = NULL, ...) ATTRIBUTE_PRINTF(2, 3);
102
103
104 #ifdef ASSERT
105 static bool is_sweeping(nmethod* which) { return _current.method() == which; }
106 // Keep track of sweeper activity in the ring buffer
107 static void record_sweep(nmethod* nm, int line);
108 static void report_events(int id, address entry);
109 static void report_events();
110 #endif
111
112 static void mark_active_nmethods(); // Invoked at the end of each safepoint
113 static void sweeper_loop();
114 static void notify(int code_blob_type); // Possibly start the sweeper thread.
115
116 static int hotness_counter_reset_val();
117 static void report_state_change(nmethod* nm);
118 static void possibly_enable_sweeper();
119 static void possibly_flush(nmethod* nm);
120 static void print(); // Printing/debugging
121 };
122
123 #endif // SHARE_VM_RUNTIME_SWEEPER_HPP