1/*
2 * Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
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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
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23 */
24
25#ifndef SHARE_RUNTIME_SWEEPER_HPP
26#define SHARE_RUNTIME_SWEEPER_HPP
27
28class WhiteBox;
29
30#include "code/codeCache.hpp"
31#include "utilities/ticks.hpp"
32
33class CodeBlobClosure;
34
35// An NmethodSweeper is an incremental cleaner for:
36// - cleanup inline caches
37// - reclamation of nmethods
38// Removing nmethods from the code cache includes two operations
39// 1) mark active nmethods
40// Is done in 'mark_active_nmethods()'. This function is called at a
41// safepoint and marks all nmethods that are active on a thread's stack.
42// 2) sweep nmethods
43// Is done in sweep_code_cache(). This function is the only place in the
44// sweeper where memory is reclaimed. Note that sweep_code_cache() is not
45// called at a safepoint. However, sweep_code_cache() stops executing if
46// another thread requests a safepoint. Consequently, 'mark_active_nmethods()'
47// and sweep_code_cache() cannot execute at the same time.
48// To reclaim memory, nmethods are first marked as 'not-entrant'. Methods can
49// be made not-entrant by (i) the sweeper, (ii) deoptimization, (iii) dependency
50// invalidation, and (iv) being replaced by a different method version (tiered
51// compilation). Not-entrant nmethods cannot be called by Java threads, but they
52// can still be active on the stack. To ensure that active nmethods are not reclaimed,
53// we have to wait until the next marking phase has completed. If a not-entrant
54// nmethod was NOT marked as active, it can be converted to 'zombie' state. To safely
55// remove the nmethod, all inline caches (IC) that point to the nmethod must be
56// cleared. After that, the nmethod can be evicted from the code cache. Each nmethod's
57// state change happens during separate sweeps. It may take at least 3 sweeps before an
58// nmethod's space is freed.
59
60class NMethodSweeper : public AllStatic {
61 private:
62 enum MethodStateChange {
63 None,
64 MadeZombie,
65 Flushed
66 };
67 static long _traversals; // Stack scan count, also sweep ID.
68 static long _total_nof_code_cache_sweeps; // Total number of full sweeps of the code cache
69 static long _time_counter; // Virtual time used to periodically invoke sweeper
70 static long _last_sweep; // Value of _time_counter when the last sweep happened
71 static CompiledMethodIterator _current; // Current compiled method
72 static int _seen; // Nof. nmethod we have currently processed in current pass of CodeCache
73
74 static volatile int _sweep_started; // Flag to control conc sweeper
75 static volatile bool _should_sweep; // Indicates if we should invoke the sweeper
76 static volatile bool _force_sweep; // Indicates if we should force a sweep
77 static volatile int _bytes_changed; // Counts the total nmethod size if the nmethod changed from:
78 // 1) alive -> not_entrant
79 // 2) not_entrant -> zombie
80 // Stat counters
81 static long _total_nof_methods_reclaimed; // Accumulated nof methods flushed
82 static long _total_nof_c2_methods_reclaimed; // Accumulated nof C2-compiled methods flushed
83 static size_t _total_flushed_size; // Total size of flushed methods
84 static int _hotness_counter_reset_val;
85
86 static Tickspan _total_time_sweeping; // Accumulated time sweeping
87 static Tickspan _total_time_this_sweep; // Total time this sweep
88 static Tickspan _peak_sweep_time; // Peak time for a full sweep
89 static Tickspan _peak_sweep_fraction_time; // Peak time sweeping one fraction
90
91 static MethodStateChange process_compiled_method(CompiledMethod *nm);
92
93 static void init_sweeper_log() NOT_DEBUG_RETURN;
94 static bool wait_for_stack_scanning();
95 static void sweep_code_cache();
96 static void handle_safepoint_request();
97 static void do_stack_scanning();
98 static void possibly_sweep();
99 public:
100 static long traversal_count() { return _traversals; }
101 static int total_nof_methods_reclaimed() { return _total_nof_methods_reclaimed; }
102 static const Tickspan total_time_sweeping() { return _total_time_sweeping; }
103 static const Tickspan peak_sweep_time() { return _peak_sweep_time; }
104 static const Tickspan peak_sweep_fraction_time() { return _peak_sweep_fraction_time; }
105 static void log_sweep(const char* msg, const char* format = NULL, ...) ATTRIBUTE_PRINTF(2, 3);
106
107
108#ifdef ASSERT
109 // Keep track of sweeper activity in the ring buffer
110 static void record_sweep(CompiledMethod* nm, int line);
111 static void report_events(int id, address entry);
112 static void report_events();
113#endif
114
115 static void mark_active_nmethods(); // Invoked at the end of each safepoint
116 static CodeBlobClosure* prepare_mark_active_nmethods();
117 static CodeBlobClosure* prepare_reset_hotness_counters();
118 static void sweeper_loop();
119 static void notify(int code_blob_type); // Possibly start the sweeper thread.
120 static void force_sweep();
121
122 static int hotness_counter_reset_val();
123 static void report_state_change(nmethod* nm);
124 static void possibly_enable_sweeper();
125 static void possibly_flush(nmethod* nm);
126 static void print(outputStream* out); // Printing/debugging
127 static void print() { print(tty); }
128};
129
130#endif // SHARE_RUNTIME_SWEEPER_HPP
131