1 /* -----------------------------------------------------------------------------
3 * (c) The GHC Team, 1995-1999
5 * Interval timer for profiling and pre-emptive scheduling.
7 * ---------------------------------------------------------------------------*/
10 * The interval timer is used for profiling and for context switching in the
11 * threaded build. Though POSIX 1003.1b includes a standard interface for
12 * such things, no one really seems to be implementing them yet. Even
13 * Solaris 2.3 only seems to provide support for @CLOCK_REAL@, whereas we're
14 * keen on getting access to @CLOCK_VIRTUAL@.
16 * Hence, we use the old-fashioned @setitimer@ that just about everyone seems
17 * to support. So much for standards.
23 #include "Proftimer.h"
26 /* As recommended in the autoconf manual */
27 # ifdef TIME_WITH_SYS_TIME
28 # include <sys/time.h>
31 # ifdef HAVE_SYS_TIME_H
32 # include <sys/time.h>
44 * In the threaded RTS, we can't set the virtual timer because the
45 * thread which has the virtual timer might be sitting waiting for a
46 * capability, and the virtual timer only ticks in CPU time.
48 * So, possible solutions:
50 * (1) tick in realtime. Not very good, because this ticker is used for
51 * profiling, and this will give us unreliable time profiling
52 * results. Furthermore, this requires picking a single OS thread
53 * to be the timekeeper, which is a bad idea because the thread in
54 * question might just be making a temporary call into Haskell land.
56 * (2) save/restore the virtual timer around excursions into STG land.
57 * Sounds great, but I tried it and the resolution of the virtual timer
58 * isn't good enough (on Linux) - most of our excursions fall
59 * within the timer's resolution and we never make any progress.
61 * (3) have a virtual timer in every OS thread. Might be reasonable,
62 * because most of the time there is only ever one of these
63 * threads running, so it approximates a single virtual timer.
64 * But still quite bogus (and I got crashes when I tried this).
66 * For now, we're using (1), but this needs a better solution. --SDM
68 #ifdef RTS_SUPPORTS_THREADS
69 #define ITIMER_FLAVOUR ITIMER_REAL
70 #define ITIMER_SIGNAL SIGALRM
72 #define ITIMER_FLAVOUR ITIMER_VIRTUAL
73 #define ITIMER_SIGNAL SIGVTALRM
78 install_vtalrm_handler(TickProc handle_tick)
80 struct sigaction action;
82 action.sa_handler = handle_tick;
84 sigemptyset(&action.sa_mask);
87 return sigaction(ITIMER_SIGNAL, &action, NULL);
91 startTicker(nat ms, TickProc handle_tick)
93 # ifndef HAVE_SETITIMER
94 /* debugBelch("No virtual timer on this system\n"); */
99 install_vtalrm_handler(handle_tick);
101 timestamp = getourtimeofday();
103 it.it_value.tv_sec = ms / 1000;
104 it.it_value.tv_usec = 1000 * (ms - (1000 * it.it_value.tv_sec));
105 it.it_interval = it.it_value;
106 return (setitimer(ITIMER_FLAVOUR, &it, NULL));
113 # ifndef HAVE_SETITIMER
114 /* debugBelch("No virtual timer on this system\n"); */
119 it.it_value.tv_sec = 0;
120 it.it_value.tv_usec = 0;
121 it.it_interval = it.it_value;
122 return (setitimer(ITIMER_FLAVOUR, &it, NULL));
127 /* This is a potential POSIX version */
132 struct itimerspec it;
135 timestamp = getourtimeofday();
137 se.sigev_notify = SIGEV_SIGNAL;
138 se.sigev_signo = ITIMER_SIGNAL;
139 se.sigev_value.sival_int = ITIMER_SIGNAL;
140 if (timer_create(CLOCK_VIRTUAL, &se, &tid)) {
141 barf("can't create virtual timer");
143 it.it_value.tv_sec = ms / 1000;
144 it.it_value.tv_nsec = 1000000 * (ms - 1000 * it.it_value.tv_sec);
145 it.it_interval = it.it_value;
146 return timer_settime(tid, TIMER_RELTIME, &it, NULL);
153 struct itimerspec it;
156 timestamp = getourtimeofday();
158 se.sigev_notify = SIGEV_SIGNAL;
159 se.sigev_signo = ITIMER_SIGNAL;
160 se.sigev_value.sival_int = ITIMER_SIGNAL;
161 if (timer_create(CLOCK_VIRTUAL, &se, &tid)) {
162 barf("can't create virtual timer");
164 it.it_value.tv_sec = 0;
165 it.it_value.tv_nsec = 0;
166 it.it_interval = it.it_value;
167 return timer_settime(tid, TIMER_RELTIME, &it, NULL);
172 /* Currently unused */
174 block_vtalrm_signal(void)
178 sigemptyset(&signals);
179 sigaddset(&signals, ITIMER_SIGNAL);
181 (void) sigprocmask(SIG_BLOCK, &signals, NULL);
185 unblock_vtalrm_signal(void)
189 sigemptyset(&signals);
190 sigaddset(&signals, ITIMER_SIGNAL);
192 (void) sigprocmask(SIG_UNBLOCK, &signals, NULL);
196 /* gettimeofday() takes around 1us on our 500MHz PIII. Since we're
197 * only calling it 50 times/s, it shouldn't have any great impact.
200 getourtimeofday(void)
203 gettimeofday(&tv, (struct timezone *) NULL);
204 // cast to lnat because nat may be 64 bit when int is only 32 bit
205 return ((lnat)tv.tv_sec * TICK_FREQUENCY +
206 (lnat)tv.tv_usec * TICK_FREQUENCY / 1000000);