1 /*
2 * Copyright Amazon.com Inc. 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.
18 *
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
21 * questions.
22 *
23 */
24
25 #ifndef SHARE_GC_SHENANDOAH_SHENANDOAHCONTROLLER_HPP
26 #define SHARE_GC_SHENANDOAH_SHENANDOAHCONTROLLER_HPP
27
28 #include "gc/shared/gcCause.hpp"
29 #include "gc/shared/concurrentGCThread.hpp"
30 #include "gc/shenandoah/shenandoahAllocRequest.hpp"
31 #include "gc/shenandoah/shenandoahSharedVariables.hpp"
32
33 /**
34 * This interface exposes methods necessary for the heap to interact
35 * with the threads responsible for driving the collection cycle.
36 */
37 class ShenandoahController: public ConcurrentGCThread {
38 private:
39 ShenandoahSharedFlag _graceful_shutdown;
40
41 shenandoah_padding(0);
42 volatile size_t _allocs_seen;
43 shenandoah_padding(1);
44 volatile size_t _gc_id;
45 shenandoah_padding(2);
46
47 protected:
48 ShenandoahSharedFlag _alloc_failure_gc;
49 ShenandoahSharedFlag _humongous_alloc_failure_gc;
50
51 // While we could have a single lock for these, it may risk unblocking
52 // GC waiters when alloc failure GC cycle finishes. We want instead
53 // to make complete explicit cycle for demanding customers.
54 Monitor _alloc_failure_waiters_lock;
55 Monitor _gc_waiters_lock;
56
57 public:
58 ShenandoahController():
59 ConcurrentGCThread(),
60 _allocs_seen(0),
61 _gc_id(0),
62 _alloc_failure_waiters_lock(Mutex::safepoint-2, "ShenandoahAllocFailureGC_lock", true),
63 _gc_waiters_lock(Mutex::safepoint-2, "ShenandoahRequestedGC_lock", true)
64 { }
65
66 // Request a collection cycle. This handles "explicit" gc requests
67 // like System.gc and "implicit" gc requests, like metaspace oom.
68 virtual void request_gc(GCCause::Cause cause) = 0;
69
70 // This cancels the collection cycle and has an option to block
71 // until another cycle runs and clears the alloc failure gc flag.
72 void handle_alloc_failure(ShenandoahAllocRequest& req, bool block);
73
74 // Invoked for allocation failures during evacuation. This cancels
75 // the collection cycle without blocking.
76 void handle_alloc_failure_evac(size_t words);
77
78 // Return true if setting the flag which indicates allocation failure succeeds.
79 bool try_set_alloc_failure_gc(bool is_humongous);
80
81 // Notify threads waiting for GC to complete.
82 void notify_alloc_failure_waiters();
83
84 // True if allocation failure flag has been set.
85 bool is_alloc_failure_gc();
86
87 // This is called for every allocation. The control thread accumulates
88 // this value when idle. During the gc cycle, the control resets it
89 // and reports it to the pacer.
90 void pacing_notify_alloc(size_t words);
91 size_t reset_allocs_seen();
92
93 // These essentially allows to cancel a collection cycle for the
94 // purpose of shutting down the JVM, without trying to start a degenerated
95 // cycle.
96 void prepare_for_graceful_shutdown();
97 bool in_graceful_shutdown();
98
99
100 // Returns the internal gc count used by the control thread. Probably
101 // doesn't need to be exposed.
102 size_t get_gc_id();
103 void update_gc_id();
104 };
105 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHCONTROLLER_HPP