1 : /* ***** BEGIN LICENSE BLOCK *****
2 : * Version: MPL 1.1/GPL 2.0/LGPL 2.1
3 : *
4 : * The contents of this file are subject to the Mozilla Public License Version
5 : * 1.1 (the "License"); you may not use this file except in compliance with
6 : * the License. You may obtain a copy of the License at
7 : * http://www.mozilla.org/MPL/
8 : *
9 : * Software distributed under the License is distributed on an "AS IS" basis,
10 : * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
11 : * for the specific language governing rights and limitations under the
12 : * License.
13 : *
14 : * The Original Code is mozilla.org code.
15 : *
16 : * The Initial Developer of the Original Code is
17 : * The Mozilla Foundation.
18 : * Portions created by the Initial Developer are Copyright (C) 2011
19 : * the Initial Developer. All Rights Reserved.
20 : *
21 : * Contributor(s):
22 : * Ted Mielczarek <ted.mielczarek@gmail.com>
23 : *
24 : * Alternatively, the contents of this file may be used under the terms of
25 : * either the GNU General Public License Version 2 or later (the "GPL"), or
26 : * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
27 : * in which case the provisions of the GPL or the LGPL are applicable instead
28 : * of those above. If you wish to allow use of your version of this file only
29 : * under the terms of either the GPL or the LGPL, and not to allow others to
30 : * use your version of this file under the terms of the MPL, indicate your
31 : * decision by deleting the provisions above and replace them with the notice
32 : * and other provisions required by the GPL or the LGPL. If you do not delete
33 : * the provisions above, a recipient may use your version of this file under
34 : * the terms of any one of the MPL, the GPL or the LGPL.
35 : *
36 : * ***** END LICENSE BLOCK ***** */
37 :
38 : /*
39 : * Event loop instrumentation. This code attempts to measure the
40 : * latency of the UI-thread event loop by firing native events at it from
41 : * a background thread, and measuring how long it takes for them
42 : * to be serviced. The measurement interval (kMeasureInterval, below)
43 : * is also used as the upper bound of acceptable response time.
44 : * When an event takes longer than that interval to be serviced,
45 : * a sample will be written to the log.
46 : *
47 : * Usage:
48 : *
49 : * Set MOZ_INSTRUMENT_EVENT_LOOP=1 in the environment to enable
50 : * this instrumentation. Currently only the UI process is instrumented.
51 : *
52 : * Set MOZ_INSTRUMENT_EVENT_LOOP_OUTPUT in the environment to a
53 : * file path to contain the log output, the default is to log to stdout.
54 : *
55 : * Set MOZ_INSTRUMENT_EVENT_LOOP_THRESHOLD in the environment to an
56 : * integer number of milliseconds to change the threshold for reporting.
57 : * The default is 20 milliseconds. Unresponsive periods shorter than this
58 : * threshold will not be reported.
59 : *
60 : * Set MOZ_INSTRUMENT_EVENT_LOOP_INTERVAL in the environment to an
61 : * integer number of milliseconds to change the maximum sampling frequency.
62 : * This variable controls how often events will be sent to the main
63 : * thread's event loop to sample responsiveness. The sampler will not
64 : * send events twice within LOOP_INTERVAL milliseconds.
65 : * The default is 10 milliseconds.
66 : *
67 : * All logged output lines start with MOZ_EVENT_TRACE. All timestamps
68 : * output are milliseconds since the epoch (PRTime / 1000).
69 : *
70 : * On startup, a line of the form:
71 : * MOZ_EVENT_TRACE start <timestamp>
72 : * will be output.
73 : *
74 : * On shutdown, a line of the form:
75 : * MOZ_EVENT_TRACE stop <timestamp>
76 : * will be output.
77 : *
78 : * When an event servicing time exceeds the threshold, a line of the form:
79 : * MOZ_EVENT_TRACE sample <timestamp> <duration>
80 : * will be output, where <duration> is the number of milliseconds that
81 : * it took for the event to be serviced.
82 : */
83 :
84 : #include "sampler.h"
85 :
86 : #include "EventTracer.h"
87 :
88 : #include <stdio.h>
89 :
90 : #include "mozilla/TimeStamp.h"
91 : #include "mozilla/WidgetTraceEvent.h"
92 : #include <limits.h>
93 : #include <prenv.h>
94 : #include <prinrval.h>
95 : #include <prthread.h>
96 : #include <prtime.h>
97 :
98 : using mozilla::TimeDuration;
99 : using mozilla::TimeStamp;
100 : using mozilla::FireAndWaitForTracerEvent;
101 :
102 : namespace {
103 :
104 : PRThread* sTracerThread = NULL;
105 : bool sExit = false;
106 :
107 : /*
108 : * The tracer thread fires events at the native event loop roughly
109 : * every kMeasureInterval. It will sleep to attempt not to send them
110 : * more quickly, but if the response time is longer than kMeasureInterval
111 : * it will not send another event until the previous response is received.
112 : *
113 : * The output defaults to stdout, but can be redirected to a file by
114 : * settting the environment variable MOZ_INSTRUMENT_EVENT_LOOP_OUTPUT
115 : * to the name of a file to use.
116 : */
117 0 : void TracerThread(void *arg)
118 : {
119 : // These are the defaults. They can be overridden by environment vars.
120 : // This should be set to the maximum latency we'd like to allow
121 : // for responsiveness.
122 0 : PRIntervalTime threshold = PR_MillisecondsToInterval(20);
123 : // This is the sampling interval.
124 0 : PRIntervalTime interval = PR_MillisecondsToInterval(10);
125 :
126 0 : sExit = false;
127 0 : FILE* log = NULL;
128 0 : char* envfile = PR_GetEnv("MOZ_INSTRUMENT_EVENT_LOOP_OUTPUT");
129 0 : if (envfile) {
130 0 : log = fopen(envfile, "w");
131 : }
132 0 : if (log == NULL)
133 0 : log = stdout;
134 :
135 0 : char* thresholdenv = PR_GetEnv("MOZ_INSTRUMENT_EVENT_LOOP_THRESHOLD");
136 0 : if (thresholdenv && *thresholdenv) {
137 0 : int val = atoi(thresholdenv);
138 0 : if (val != 0 && val != INT_MAX && val != INT_MIN) {
139 0 : threshold = PR_MillisecondsToInterval(val);
140 : }
141 : }
142 :
143 0 : char* intervalenv = PR_GetEnv("MOZ_INSTRUMENT_EVENT_LOOP_INTERVAL");
144 0 : if (intervalenv && *intervalenv) {
145 0 : int val = atoi(intervalenv);
146 0 : if (val != 0 && val != INT_MAX && val != INT_MIN) {
147 0 : interval = PR_MillisecondsToInterval(val);
148 : }
149 : }
150 :
151 0 : fprintf(log, "MOZ_EVENT_TRACE start %llu\n", PR_Now() / PR_USEC_PER_MSEC);
152 :
153 0 : while (!sExit) {
154 0 : TimeStamp start(TimeStamp::Now());
155 0 : SAMPLER_RESPONSIVENESS(start);
156 0 : PRIntervalTime next_sleep = interval;
157 :
158 : //TODO: only wait up to a maximum of interval; return
159 : // early if that threshold is exceeded and dump a stack trace
160 : // or do something else useful.
161 0 : if (FireAndWaitForTracerEvent()) {
162 0 : TimeDuration duration = TimeStamp::Now() - start;
163 : // Only report samples that exceed our measurement threshold.
164 0 : if (duration.ToMilliseconds() > threshold) {
165 : fprintf(log, "MOZ_EVENT_TRACE sample %llu %d\n",
166 0 : PR_Now() / PR_USEC_PER_MSEC,
167 0 : int(duration.ToSecondsSigDigits() * 1000));
168 : }
169 :
170 0 : if (next_sleep > duration.ToMilliseconds()) {
171 0 : next_sleep -= int(duration.ToMilliseconds());
172 : }
173 : else {
174 : // Don't sleep at all if this event took longer than the measure
175 : // interval to deliver.
176 0 : next_sleep = 0;
177 : }
178 : }
179 :
180 0 : if (next_sleep != 0 && !sExit) {
181 0 : PR_Sleep(next_sleep);
182 : }
183 : }
184 :
185 0 : fprintf(log, "MOZ_EVENT_TRACE stop %llu\n", PR_Now() / PR_USEC_PER_MSEC);
186 :
187 0 : if (log != stdout)
188 0 : fclose(log);
189 0 : }
190 :
191 : } // namespace
192 :
193 : namespace mozilla {
194 :
195 0 : bool InitEventTracing()
196 : {
197 0 : if (sTracerThread)
198 0 : return true;
199 :
200 : // Initialize the widget backend.
201 0 : if (!InitWidgetTracing())
202 0 : return false;
203 :
204 : // Create a thread that will fire events back at the
205 : // main thread to measure responsiveness.
206 0 : NS_ABORT_IF_FALSE(!sTracerThread, "Event tracing already initialized!");
207 : sTracerThread = PR_CreateThread(PR_USER_THREAD,
208 : TracerThread,
209 : NULL,
210 : PR_PRIORITY_NORMAL,
211 : PR_GLOBAL_THREAD,
212 : PR_JOINABLE_THREAD,
213 0 : 0);
214 0 : return sTracerThread != NULL;
215 : }
216 :
217 0 : void ShutdownEventTracing()
218 : {
219 0 : if (!sTracerThread)
220 0 : return;
221 :
222 0 : sExit = true;
223 : // Ensure that the tracer thread doesn't hang.
224 0 : SignalTracerThread();
225 :
226 0 : if (sTracerThread)
227 0 : PR_JoinThread(sTracerThread);
228 0 : sTracerThread = NULL;
229 :
230 : // Allow the widget backend to clean up.
231 0 : CleanUpWidgetTracing();
232 : }
233 :
234 : } // namespace mozilla
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