1 /*
2 * Copyright (c) 2019, 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.
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 #include "precompiled.hpp"
26 #include "gc/shared/gcOverheadChecker.hpp"
27 #include "gc/shared/softRefPolicy.hpp"
28 #include "logging/log.hpp"
29
30 GCOverheadChecker::GCOverheadChecker() :
31 _gc_overhead_limit_exceeded(false),
32 _print_gc_overhead_limit_would_be_exceeded(false),
33 _gc_overhead_limit_count(0) {
34 assert(GCOverheadLimitThreshold > 0,
35 "No opportunity to clear SoftReferences before GC overhead limit");
36 }
37
38 void GCOverheadChecker::check_gc_overhead_limit(GCOverheadTester* time_overhead,
39 GCOverheadTester* space_overhead,
40 bool is_full_gc,
41 GCCause::Cause gc_cause,
42 SoftRefPolicy* soft_ref_policy) {
43
44 // Ignore explicit GC's. Exiting here does not set the flag and
45 // does not reset the count.
46 if (GCCause::is_user_requested_gc(gc_cause) ||
47 GCCause::is_serviceability_requested_gc(gc_cause)) {
48 return;
49 }
50
51 bool print_gc_overhead_limit_would_be_exceeded = false;
52 if (is_full_gc) {
53 if (time_overhead->is_exceeded() && space_overhead->is_exceeded()) {
54 // Collections, on average, are taking too much time, and
55 // we have too little space available after a full gc.
56 // At this point the GC overhead limit is being exceeded.
57 _gc_overhead_limit_count++;
58 if (UseGCOverheadLimit) {
59 if (_gc_overhead_limit_count >= GCOverheadLimitThreshold){
60 // All conditions have been met for throwing an out-of-memory
61 set_gc_overhead_limit_exceeded(true);
62 // Avoid consecutive OOM due to the gc time limit by resetting
63 // the counter.
64 reset_gc_overhead_limit_count();
65 } else {
66 // The required consecutive collections which exceed the
67 // GC time limit may or may not have been reached. We
68 // are approaching that condition and so as not to
69 // throw an out-of-memory before all SoftRef's have been
70 // cleared, set _should_clear_all_soft_refs in CollectorPolicy.
71 // The clearing will be done on the next GC.
72 bool near_limit = gc_overhead_limit_near();
73 if (near_limit) {
74 soft_ref_policy->set_should_clear_all_soft_refs(true);
75 log_trace(gc, ergo)("Nearing GC overhead limit, will be clearing all SoftReference");
76 }
77 }
78 }
79 // Set this even when the overhead limit will not
80 // cause an out-of-memory. Diagnostic message indicating
81 // that the overhead limit is being exceeded is sometimes
82 // printed.
83 print_gc_overhead_limit_would_be_exceeded = true;
84
85 } else {
86 // Did not exceed overhead limits
87 reset_gc_overhead_limit_count();
88 }
89 }
90
91 if (UseGCOverheadLimit) {
92 if (gc_overhead_limit_exceeded()) {
93 log_trace(gc, ergo)("GC is exceeding overhead limit of " UINTX_FORMAT "%%", GCTimeLimit);
94 reset_gc_overhead_limit_count();
95 } else if (print_gc_overhead_limit_would_be_exceeded) {
96 assert(_gc_overhead_limit_count > 0, "Should not be printing");
97 log_trace(gc, ergo)("GC would exceed overhead limit of " UINTX_FORMAT "%% %d consecutive time(s)",
98 GCTimeLimit, _gc_overhead_limit_count);
99 }
100 }
101 }