1 /*
2 * Copyright (c) 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.
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.
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23 */
24
25 #ifndef SHARE_VM_RUNTIME_RTMLOCKING_HPP
26 #define SHARE_VM_RUNTIME_RTMLOCKING_HPP
27
28 // Generate RTM (Restricted Transactional Memory) locking code for all inflated
29 // locks when "UseRTM" option is on with normal locking mechanism as fall back
30 // handler.
31 //
32 // On abort/lock busy the lock will be retried a fixed number of times under RTM
33 // as specified by "RTMRetryCount" option. The locks which abort too often
34 // can be auto tuned or manually tuned.
35 //
36 // Auto-tuning can be done on an option like UseRTMDeopt and it will need abort
37 // ratio calculation for each lock. The abort ratio will be calculated after
38 // "RTMAbortThreshold" number of aborts is reached. The formulas are:
39 //
40 // Aborted transactions = abort_count * 100
41 // All transactions = total_count * RTMTotalCountIncrRate
42 //
43 // Aborted transactions >= All transactions * RTMAbortRatio
44 //
45 // If "UseRTMDeopt" is on and the aborts ratio reaches "RTMAbortRatio"
46 // the method containing the lock will be deoptimized and recompiled with
47 // all locks as normal locks. If the abort ratio continues to remain low after
48 // "RTMLockingThreshold" locks are attempted, then the method will be deoptimized
49 // and recompiled with all locks as RTM locks without abort ratio calculation code.
50 // The abort ratio calculation can be delayed by specifying flag
51 // -XX:RTMLockingCalculationDelay in millisecond.
52 //
53 // For manual tuning the abort statistics for each lock needs to be provided
54 // to the user on some JVM option like "PrintPreciseRTMLockingStatistics".
55 // Based on the abort statistics users can create a .hotspot_compiler file
56 // or use -XX:CompileCommnad=option,class::method,DoNotElide
57 // to specify for which methods to disable RTM locking.
58 //
59 // When UseRTMForStackLocks option is enabled along with UseRTMLocking option,
60 // the RTM locking code is generated for stack locks too.
61 // The retries, auto-tuning support and rtm locking statistics are all
62 // supported for stack locks just like inflated locks.
63
64 // RTM locking counters
65 class RTMLockingCounters VALUE_OBJ_CLASS_SPEC {
66 private:
67 uintx _total_count; // Total RTM locks count
68 uintx _abort_count; // Total aborts count
69
70 public:
71 enum { ABORT_STATUS_LIMIT = 6 };
72 // Counters per RTM Abort Status. Incremented with +PrintPreciseRTMLockingStatistics
73 // RTM uses the EAX register to communicate abort status to software.
74 // Following an RTM abort the EAX register has the following definition.
75 //
76 // EAX register bit position Meaning
77 // 0 Set if abort caused by XABORT instruction.
78 // 1 If set, the transaction may succeed on a retry. This bit is always clear if bit 0 is set.
79 // 2 Set if another logical processor conflicted with a memory address that was part of the transaction that aborted.
80 // 3 Set if an internal buffer overflowed.
81 // 4 Set if a debug breakpoint was hit.
82 // 5 Set if an abort occurred during execution of a nested transaction.
83 private:
84 uintx _abortX_count[ABORT_STATUS_LIMIT];
85
86 public:
87 static uintx _calculation_flag;
88 static uintx* rtm_calculation_flag() { return &_calculation_flag; }
89
90 static void init();
91
92 RTMLockingCounters() : _total_count(0), _abort_count(0) {
93 for (int i = 0; i < ABORT_STATUS_LIMIT; i++) {
94 _abortX_count[i] = 0;
95 }
96 }
97
98 uintx* total_count_addr() { return &_total_count; }
99 uintx* abort_count_addr() { return &_abort_count; }
100 uintx* abortX_count_addr() { return &_abortX_count[0]; }
101
102 static int total_count_offset() { return (int)offset_of(RTMLockingCounters, _total_count); }
103 static int abort_count_offset() { return (int)offset_of(RTMLockingCounters, _abort_count); }
104 static int abortX_count_offset() { return (int)offset_of(RTMLockingCounters, _abortX_count[0]); }
105
106
107 bool nonzero() { return (_abort_count+_total_count) > 0; }
108
109 void print_on(outputStream* st);
110 void print() { print_on(tty); }
111 };
112
113 #endif // SHARE_VM_RUNTIME_RTMLOCKING_HPP