author | stefank |
Wed, 22 May 2019 13:06:31 +0200 | |
changeset 54983 | 81becad91321 |
parent 50113 | caf115bb98ad |
child 58041 | d8902e9c307c |
child 58678 | 9cf78a70fa4f |
permissions | -rw-r--r-- |
50113 | 1 |
/* |
2 |
* Copyright (c) 2013, 2018, 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 "rdtsc_x86.hpp" |
|
27 |
#include "runtime/thread.inline.hpp" |
|
28 |
#include "vm_version_ext_x86.hpp" |
|
29 |
||
30 |
// The following header contains the implementations of rdtsc() |
|
31 |
#include OS_CPU_HEADER_INLINE(os) |
|
32 |
||
33 |
static jlong _epoch = 0; |
|
34 |
static bool rdtsc_elapsed_counter_enabled = false; |
|
35 |
static jlong tsc_frequency = 0; |
|
36 |
||
37 |
static jlong set_epoch() { |
|
38 |
assert(0 == _epoch, "invariant"); |
|
39 |
_epoch = os::rdtsc(); |
|
40 |
return _epoch; |
|
41 |
} |
|
42 |
||
43 |
// Base loop to estimate ticks frequency for tsc counter from user mode. |
|
44 |
// Volatiles and sleep() are used to prevent compiler from applying optimizations. |
|
45 |
static void do_time_measurements(volatile jlong& time_base, |
|
46 |
volatile jlong& time_fast, |
|
47 |
volatile jlong& time_base_elapsed, |
|
48 |
volatile jlong& time_fast_elapsed) { |
|
49 |
static const unsigned int FT_SLEEP_MILLISECS = 1; |
|
50 |
const unsigned int loopcount = 3; |
|
51 |
||
52 |
volatile jlong start = 0; |
|
53 |
volatile jlong fstart = 0; |
|
54 |
volatile jlong end = 0; |
|
55 |
volatile jlong fend = 0; |
|
56 |
||
57 |
// Figure out the difference between rdtsc and os provided timer. |
|
58 |
// base algorithm adopted from JRockit. |
|
59 |
for (unsigned int times = 0; times < loopcount; times++) { |
|
60 |
start = os::elapsed_counter(); |
|
61 |
OrderAccess::fence(); |
|
62 |
fstart = os::rdtsc(); |
|
63 |
||
64 |
// use sleep to prevent compiler from optimizing |
|
65 |
os::sleep(Thread::current(), FT_SLEEP_MILLISECS, true); |
|
66 |
||
67 |
end = os::elapsed_counter(); |
|
68 |
OrderAccess::fence(); |
|
69 |
fend = os::rdtsc(); |
|
70 |
||
71 |
time_base += end - start; |
|
72 |
time_fast += fend - fstart; |
|
73 |
||
74 |
// basis for calculating the os tick start |
|
75 |
// to fast time tick start offset |
|
76 |
time_base_elapsed += end; |
|
77 |
time_fast_elapsed += (fend - _epoch); |
|
78 |
} |
|
79 |
||
80 |
time_base /= loopcount; |
|
81 |
time_fast /= loopcount; |
|
82 |
time_base_elapsed /= loopcount; |
|
83 |
time_fast_elapsed /= loopcount; |
|
84 |
} |
|
85 |
||
86 |
static jlong initialize_frequency() { |
|
87 |
assert(0 == tsc_frequency, "invariant"); |
|
88 |
assert(0 == _epoch, "invariant"); |
|
89 |
const jlong initial_counter = set_epoch(); |
|
90 |
if (initial_counter == 0) { |
|
91 |
return 0; |
|
92 |
} |
|
93 |
// os time frequency |
|
94 |
static double os_freq = (double)os::elapsed_frequency(); |
|
95 |
assert(os_freq > 0, "os_elapsed frequency corruption!"); |
|
96 |
||
97 |
double tsc_freq = .0; |
|
98 |
double os_to_tsc_conv_factor = 1.0; |
|
99 |
||
100 |
// if platform supports invariant tsc, |
|
101 |
// apply higher resolution and granularity for conversion calculations |
|
102 |
if (VM_Version_Ext::supports_tscinv_ext()) { |
|
103 |
// for invariant tsc platforms, take the maximum qualified cpu frequency |
|
104 |
tsc_freq = (double)VM_Version_Ext::maximum_qualified_cpu_frequency(); |
|
105 |
os_to_tsc_conv_factor = tsc_freq / os_freq; |
|
106 |
} else { |
|
107 |
// use measurements to estimate |
|
108 |
// a conversion factor and the tsc frequency |
|
109 |
||
110 |
volatile jlong time_base = 0; |
|
111 |
volatile jlong time_fast = 0; |
|
112 |
volatile jlong time_base_elapsed = 0; |
|
113 |
volatile jlong time_fast_elapsed = 0; |
|
114 |
||
115 |
// do measurements to get base data |
|
116 |
// on os timer and fast ticks tsc time relation. |
|
117 |
do_time_measurements(time_base, time_fast, time_base_elapsed, time_fast_elapsed); |
|
118 |
||
119 |
// if invalid measurements, cannot proceed |
|
120 |
if (time_fast == 0 || time_base == 0) { |
|
121 |
return 0; |
|
122 |
} |
|
123 |
||
124 |
os_to_tsc_conv_factor = (double)time_fast / (double)time_base; |
|
125 |
if (os_to_tsc_conv_factor > 1) { |
|
126 |
// estimate on tsc counter frequency |
|
127 |
tsc_freq = os_to_tsc_conv_factor * os_freq; |
|
128 |
} |
|
129 |
} |
|
130 |
||
131 |
if ((tsc_freq < 0) || (tsc_freq > 0 && tsc_freq <= os_freq) || (os_to_tsc_conv_factor <= 1)) { |
|
132 |
// safer to run with normal os time |
|
133 |
tsc_freq = .0; |
|
134 |
} |
|
135 |
||
136 |
// frequency of the tsc_counter |
|
137 |
return (jlong)tsc_freq; |
|
138 |
} |
|
139 |
||
140 |
static bool initialize_elapsed_counter() { |
|
141 |
tsc_frequency = initialize_frequency(); |
|
142 |
return tsc_frequency != 0 && _epoch != 0; |
|
143 |
} |
|
144 |
||
145 |
static bool ergonomics() { |
|
146 |
const bool invtsc_support = Rdtsc::is_supported(); |
|
147 |
if (FLAG_IS_DEFAULT(UseFastUnorderedTimeStamps) && invtsc_support) { |
|
54983
81becad91321
8224203: Remove need to specify type when using FLAG_SET macros
stefank
parents:
50113
diff
changeset
|
148 |
FLAG_SET_ERGO(UseFastUnorderedTimeStamps, true); |
50113 | 149 |
} |
150 |
||
151 |
bool ft_enabled = UseFastUnorderedTimeStamps && invtsc_support; |
|
152 |
||
153 |
if (!ft_enabled) { |
|
154 |
if (UseFastUnorderedTimeStamps && VM_Version::supports_tsc()) { |
|
155 |
warning("\nThe hardware does not support invariant tsc (INVTSC) register and/or cannot guarantee tsc synchronization between sockets at startup.\n"\ |
|
156 |
"Values returned via rdtsc() are not guaranteed to be accurate, esp. when comparing values from cross sockets reads. Enabling UseFastUnorderedTimeStamps on non-invariant tsc hardware should be considered experimental.\n"); |
|
157 |
ft_enabled = true; |
|
158 |
} |
|
159 |
} |
|
160 |
||
161 |
if (!ft_enabled) { |
|
162 |
// Warn if unable to support command-line flag |
|
163 |
if (UseFastUnorderedTimeStamps && !VM_Version::supports_tsc()) { |
|
164 |
warning("Ignoring UseFastUnorderedTimeStamps, hardware does not support normal tsc"); |
|
165 |
} |
|
166 |
} |
|
167 |
||
168 |
return ft_enabled; |
|
169 |
} |
|
170 |
||
171 |
bool Rdtsc::is_supported() { |
|
172 |
return VM_Version_Ext::supports_tscinv_ext(); |
|
173 |
} |
|
174 |
||
175 |
bool Rdtsc::is_elapsed_counter_enabled() { |
|
176 |
return rdtsc_elapsed_counter_enabled; |
|
177 |
} |
|
178 |
||
179 |
jlong Rdtsc::frequency() { |
|
180 |
return tsc_frequency; |
|
181 |
} |
|
182 |
||
183 |
jlong Rdtsc::elapsed_counter() { |
|
184 |
return os::rdtsc() - _epoch; |
|
185 |
} |
|
186 |
||
187 |
jlong Rdtsc::epoch() { |
|
188 |
return _epoch; |
|
189 |
} |
|
190 |
||
191 |
jlong Rdtsc::raw() { |
|
192 |
return os::rdtsc(); |
|
193 |
} |
|
194 |
||
195 |
bool Rdtsc::initialize() { |
|
196 |
static bool initialized = false; |
|
197 |
if (!initialized) { |
|
198 |
assert(!rdtsc_elapsed_counter_enabled, "invariant"); |
|
199 |
VM_Version_Ext::initialize(); |
|
200 |
assert(0 == tsc_frequency, "invariant"); |
|
201 |
assert(0 == _epoch, "invariant"); |
|
202 |
bool result = initialize_elapsed_counter(); // init hw |
|
203 |
if (result) { |
|
204 |
result = ergonomics(); // check logical state |
|
205 |
} |
|
206 |
rdtsc_elapsed_counter_enabled = result; |
|
207 |
initialized = true; |
|
208 |
} |
|
209 |
return rdtsc_elapsed_counter_enabled; |
|
210 |
} |