Hello!
Since I joinded this list, I compiled from source (on RHEL4, RHEL5 and Debian 4; 32 and 64 bit arhitectures) various versions of gambit-c. The tests 4 and 6 from make check have given values close to the expected ones for heartbeat frequency, EXCEPT for the latest few versions of gambit-c. (I don't remember the last good one)
For the v4.3.0, regardless of the configuration options I use (--enable-single-host --enable-gcc-opts --enable-inline-jumps --enable-shared), the architecture (32/64 bits, amd/intel), I get ~ 40 Hz instead of close to 500 Hz expected.
Why ?
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On 23-Oct-08, at 7:47 AM, Cristian Baboi wrote:
Hello!
Since I joinded this list, I compiled from source (on RHEL4, RHEL5 and Debian 4; 32 and 64 bit arhitectures) various versions of gambit-c. The tests 4 and 6 from make check have given values close to the expected ones for heartbeat frequency, EXCEPT for the latest few versions of gambit-c. (I don't remember the last good one)
For the v4.3.0, regardless of the configuration options I use (--enable-single-host --enable-gcc-opts --enable-inline-jumps --enable-shared), the architecture (32/64 bits, amd/intel), I get ~ 40 Hz instead of close to 500 Hz expected.
Why ?
This bug was introduced when I changed the default thread priority to be 0. The program tests/mix.scm which tests the heartbeat interrupts did it with a thread whose priority was also set to 0 (which means the primordial thread and the heartbeat thread were being interleaved instead of the heartbeat thread running as soon as there was a heartbeat interrupt). Note: the heartbeat interrupts on Unix system are obtained using the ITIMER_VIRTUAL timer (i.e. the interval is in user time, not real time).
So on Linux the test for heartbeat interrupts should be back to normal. On Mac OS X the heartbeat interval is really not accurate, but it is the fault of the operating system... To test this out I wrote the program below. Read the comments for details.
To everyone on the list, if you have a non-Linux flavor of Unix (or an unusual Linux distribution or hardware), could you please try it out on your system and report any anomalies.
To those knowing how to report bugs to Apple, could you?
Marc
/* * File: "timer-perf.c". * * This program was written by Marc Feeley (feeley@iro.umontreal.ca). * * This program tests the accuracy of the ITIMER_VIRTUAL and ITIMER_REAL * timers. When the setitimer is used to request a given timer interval * the system will setup the timer to deliver a "heartbeat interrupt" * at a certain interval, which generally is not exactly the one * requested (because the timers have a certain granularity and a * minimal interval). With a call to getitimer it is possible to * determine which interval was set by the OS (the "claimed" interval). * * In this test, "accuracy" is measured as the ratio between the * claimed interval and the actual interval obtained. The tests * on Mac OS X and Linux show that the timer granularity, minimal * interval and accuracy vary considerably between these operating * systems. * * Execution on Mac OS X 10.5.5 on a Mac Book Pro with Intel Core Duo: * * % gcc timer-perf.c * % time ./a.out * ITIMER_REAL: requested, claimed and actual intervals in us and accuracy * 100000 100000 101318 (101%) * 50000 50000 50061 (100%) * 20000 20000 19884 (99%) * 10000 10000 9945 (99%) * 5000 5000 4957 (99%) * 2000 2000 1970 (98%) * 1000 1000 979 (97%) * 500 500 482 (96%) * 200 200 183 (91%) * 100 100 86 (86%) * ITIMER_VIRTUAL: requested, claimed and actual intervals in us and accuracy * 100000 100000 103766 (103%) * 50000 50000 52527 (105%) * 20000 20000 22161 (110%) * 10000 10000 11818 (118%) * 5000 5000 7286 (145%) * 2000 2000 4527 (226%) * 1000 1000 3141 (314%) * 500 500 2762 (552%) * 200 200 2333 (1166%) * 100 100 2407 (2407%) * done (dummy = 1566934064) * * real 1m27.405s * user 1m25.414s * sys 0m1.516s * * Execution on Linux: * * % gcc timer-perf.c * % time ./a.out * ITIMER_REAL: requested, claimed and actual intervals in us and accuracy * 100000 100000 104387 (104%) * 50000 50000 50639 (101%) * 20000 20000 20074 (100%) * 10000 10000 10037 (100%) * 5000 5000 5018 (100%) * 2000 2000 4000 (200%) * 1000 1000 4007 (400%) * 500 500 4007 (801%) * 200 200 3978 (1989%) * 100 100 4000 (4000%) * ITIMER_VIRTUAL: requested, claimed and actual intervals in us and accuracy * 100000 100006 104197 (104%) * 50000 52003 52098 (100%) * 20000 20001 20142 (100%) * 10000 12000 12043 (100%) * 5000 8000 8029 (100%) * 2000 4000 4007 (100%) * done (dummy = 2132937504) * * real 0m35.339s * user 0m35.302s * sys 0m0.000s */
#include <sys/time.h> #include <signal.h> #include <stdio.h> #include <unistd.h> #include <sys/resource.h>
int dummy; int count;
void heartbeat_interrupt_handler( int sig ) { count++; }
int setup_heartbeat( int timer, int usecs ) { struct itimerval tv; struct sigaction act; int secs = 0; int SIG;
if (timer == ITIMER_REAL) SIG = SIGALRM; else SIG = SIGVTALRM;
if (usecs == 0) act.sa_handler = SIG_IGN; else act.sa_handler = heartbeat_interrupt_handler;
act.sa_flags = 0; #ifdef SA_INTERRUPT act.sa_flags |= SA_INTERRUPT; #endif sigemptyset( &act.sa_mask ); sigaction( SIG, &act, 0 );
tv.it_interval.tv_sec = secs; tv.it_interval.tv_usec = usecs; tv.it_value.tv_sec = secs; tv.it_value.tv_usec = usecs; setitimer( timer, &tv, 0 ); getitimer( timer, &tv );
return tv.it_interval.tv_usec; }
int fib( int n ) { if (n < 2) return count; else return fib( n-1 ) + fib( n-2 ); }
void waste_time() { dummy = fib( 40 ); }
void test( int timer ) { int usecs = 100000; /* 0.1 second */ int div_seq = 0; int last_usecs = 0; int this_usecs; struct rusage start; struct rusage end; int duration;
if (timer == ITIMER_REAL) printf( "ITIMER_REAL" ); else printf( "ITIMER_VIRTUAL" );
printf( ": requested, claimed and actual intervals in us and accuracy\n" );
for (;;) { count = 0; this_usecs = setup_heartbeat( timer, usecs ); if (this_usecs == last_usecs || this_usecs < 100) { setup_heartbeat( timer, 0 ); break; } getrusage( RUSAGE_SELF, &start ); waste_time(); getrusage( RUSAGE_SELF, &end ); setup_heartbeat( timer, 0 ); duration = (end.ru_utime.tv_sec*1000000 + end.ru_utime.tv_usec) - (start.ru_utime.tv_sec*1000000 + start.ru_utime.tv_usec); printf( " %8d %8d %8d (%d%%)\n", usecs, this_usecs, duration/ count, 100*duration/(count*this_usecs) ); last_usecs = this_usecs; switch (div_seq++) { case 0: usecs = usecs / 2; break; case 1: usecs = usecs * 2 / 5; break; case 2: usecs = usecs / 2; div_seq = 0; break; } } }
int main( int argc, char *argv[] ) { test( ITIMER_REAL ); test( ITIMER_VIRTUAL ); printf( "done (dummy = %d)\n", dummy ); return 0; }
On Thu, 23 Oct 2008 18:10:50 +0300, Marc Feeley feeley@iro.umontreal.ca wrote:
/*
- File: "timer-perf.c".
- This program was written by Marc Feeley (feeley@iro.umontreal.ca).
- This program tests the accuracy of the ITIMER_VIRTUAL and ITIMER_REAL
- timers. When the setitimer is used to request a given timer interval
- the system will setup the timer to deliver a "heartbeat interrupt"
- at a certain interval, which generally is not exactly the one
- requested (because the timers have a certain granularity and a
- minimal interval). With a call to getitimer it is possible to
- determine which interval was set by the OS (the "claimed" interval).
- In this test, "accuracy" is measured as the ratio between the
- claimed interval and the actual interval obtained. The tests
- on Mac OS X and Linux show that the timer granularity, minimal
- interval and accuracy vary considerably between these operating
- systems.
- Execution on Mac OS X 10.5.5 on a Mac Book Pro with Intel Core Duo:
- % gcc timer-perf.c
- % time ./a.out
- ITIMER_REAL: requested, claimed and actual intervals in us and
accuracy
100000 100000 101318 (101%)50000 50000 50061 (100%)20000 20000 19884 (99%)10000 10000 9945 (99%)5000 5000 4957 (99%)2000 2000 1970 (98%)1000 1000 979 (97%)500 500 482 (96%)200 200 183 (91%)100 100 86 (86%)- ITIMER_VIRTUAL: requested, claimed and actual intervals in us and
accuracy
100000 100000 103766 (103%)50000 50000 52527 (105%)20000 20000 22161 (110%)10000 10000 11818 (118%)5000 5000 7286 (145%)2000 2000 4527 (226%)1000 1000 3141 (314%)500 500 2762 (552%)200 200 2333 (1166%)100 100 2407 (2407%)- done (dummy = 1566934064)
- real 1m27.405s
- user 1m25.414s
- sys 0m1.516s
- Execution on Linux:
- % gcc timer-perf.c
- % time ./a.out
- ITIMER_REAL: requested, claimed and actual intervals in us and
accuracy
100000 100000 104387 (104%)50000 50000 50639 (101%)20000 20000 20074 (100%)10000 10000 10037 (100%)5000 5000 5018 (100%)2000 2000 4000 (200%)1000 1000 4007 (400%)500 500 4007 (801%)200 200 3978 (1989%)100 100 4000 (4000%)- ITIMER_VIRTUAL: requested, claimed and actual intervals in us and
accuracy
100000 100006 104197 (104%)50000 52003 52098 (100%)20000 20001 20142 (100%)10000 12000 12043 (100%)5000 8000 8029 (100%)2000 4000 4007 (100%)- done (dummy = 2132937504)
- real 0m35.339s
- user 0m35.302s
- sys 0m0.000s
*/
Here are the results for 2 linux systems
RHEL 4.7 64 bit, 2 x intel xeon CPU 3.20GHz
Two sequential runs in foreground =================================== ITIMER_REAL: requested, claimed and actual intervals in us and accuracy 100000 100984 103615 (102%) 50000 50992 51316 (100%) 20000 20996 21019 (100%) 10000 10998 11027 (100%) 5000 5999 5819 (97%) 2000 2999 3002 (100%) 1000 1999 2000 (100%) 500 999 1000 (100%) ITIMER_VIRTUAL: requested, claimed and actual intervals in us and accuracy 100000 100984 102089 (101%) 50000 50992 52343 (102%) 20000 20996 21194 (100%) 10000 10998 11052 (100%) 5000 5999 6004 (100%) 2000 2999 3002 (100%) 1000 1999 2000 (100%) 500 999 1000 (100%) done (dummy = 1551135873)
real 0m32.383s user 0m32.311s sys 0m0.065s
ITIMER_REAL: requested, claimed and actual intervals in us and accuracy 100000 100984 102194 (101%) 50000 50992 51702 (101%) 20000 20996 21064 (100%) 10000 10998 11003 (100%) 5000 5999 6011 (100%) 2000 2999 3001 (100%) 1000 1999 2000 (100%) 500 999 1000 (100%) ITIMER_VIRTUAL: requested, claimed and actual intervals in us and accuracy 100000 100984 101603 (100%) 50000 50992 51387 (100%) 20000 20996 21189 (100%) 10000 10998 11004 (100%) 5000 5999 6005 (100%) 2000 2999 3003 (100%) 1000 1999 2001 (100%) 500 999 1000 (100%) done (dummy = 1525906181)
real 0m31.960s user 0m31.953s sys 0m0.002s
Four parallel runs in background ================================== ITIMER_REAL: requested, claimed and actual intervals in us and accuracy 100000 100984 103826 (102%) 50000 50992 51044 (100%) 20000 20996 21208 (101%) 10000 10998 11023 (100%) 5000 5999 6002 (100%) 2000 2999 3001 (100%) 1000 1999 1999 (100%) 500 999 999 (100%) ITIMER_VIRTUAL: requested, claimed and actual intervals in us and accuracy 100000 100984 102616 (101%) 50000 50992 51911 (101%) 20000 20996 21211 (101%) 10000 10998 11050 (100%) 5000 5999 6007 (100%) 2000 2999 3002 (100%) 1000 1999 2000 (100%) 500 999 1000 (100%) done (dummy = 214280170)
9 parallel runs in background ================================== ITIMER_REAL: requested, claimed and actual intervals in us and accuracy 100000 100984 52943 (52%) 50000 50992 33174 (65%) 20000 20996 17676 (84%) 10000 10998 10034 (91%) 5000 5999 5727 (95%) 2000 2999 2998 (99%) 1000 1999 2000 (100%) 500 999 999 (100%) ITIMER_VIRTUAL: requested, claimed and actual intervals in us and accuracy 100000 100984 101439 (100%) 50000 50992 51376 (100%) 20000 20996 21085 (100%) 10000 10998 11014 (100%) 5000 5999 6017 (100%) 2000 2999 3004 (100%) 1000 1999 2000 (100%) 500 999 1000 (100%) done (dummy = 680961885) ---------------------------------------------
RHEL 4.7 32 bit pentium4 2.4 GHz
Two sequential runs in foreground =================================== ITIMER_REAL: requested, claimed and actual intervals in us and accuracy 100000 100984 103219 (102%) 50000 50992 50919 (99%) 20000 20996 21068 (100%) 10000 10998 10988 (99%) 5000 5999 5988 (99%) 2000 2999 2995 (99%) 1000 1999 1995 (99%) 500 999 999 (100%) ITIMER_VIRTUAL: requested, claimed and actual intervals in us and accuracy 100000 100984 103131 (102%) 50000 50992 51624 (101%) 20000 20996 21038 (100%) 10000 10998 11017 (100%) 5000 5999 6000 (100%) 2000 2999 3001 (100%) 1000 1999 2000 (100%) 500 999 1000 (100%) done (dummy = 825648992)
real 0m56.543s user 0m56.344s sys 0m0.023s
ITIMER_REAL: requested, claimed and actual intervals in us and accuracy 100000 100984 103287 (102%) 50000 50992 51529 (101%) 20000 20996 21038 (100%) 10000 10998 10995 (99%) 5000 5999 5993 (99%) 2000 2999 2996 (99%) 1000 1999 1995 (99%) 500 999 999 (100%) ITIMER_VIRTUAL: requested, claimed and actual intervals in us and accuracy 100000 100984 103337 (102%) 50000 50992 51653 (101%) 20000 20996 21032 (100%) 10000 10998 11020 (100%) 5000 5999 6004 (100%) 2000 2999 3001 (100%) 1000 1999 2000 (100%) 500 999 1000 (100%) done (dummy = 952733829)
real 0m56.356s user 0m56.164s sys 0m0.019s
Four concurrent runs in background =================================== ITIMER_REAL: requested, claimed and actual intervals in us and accuracy 100000 100984 50292 (49%) 50000 50992 34130 (66%) 20000 20996 17724 (84%) 10000 10998 10007 (90%) 5000 5999 5735 (95%) 2000 2999 2936 (97%) 1000 1999 1966 (98%) 500 999 999 (100%) ITIMER_VIRTUAL: requested, claimed and actual intervals in us and accuracy 100000 100984 103102 (102%) 50000 50992 51712 (101%) 20000 20996 21038 (100%) 10000 10998 11023 (100%) 5000 5999 6009 (100%) 2000 2999 3001 (100%) 1000 1999 2000 (100%) 500 999 1000 (100%) done (dummy = -364232017)
________ Information from NOD32 ________ This message was checked by NOD32 Antivirus System for Linux Mail Servers. part000.txt - is OK test6.ok - is OK test4.ok - is OK http://www.eset.com
-
Cristian Baboi -
Marc Feeley