On Tue, 12 May 2009 09:33:34 +0300 Mikolaj Golub wrote:
MG> On Mon, 11 May 2009 19:00:54 +0300 Mikolaj Golub wrote:
>> Hello,
>>
>> If I run the following program
>>
>> ---------------
>>
>> #include <omp.h>
>>
>> int n = 4, m = 2;
>>
>> int main () {
>> for (;;) {
>> int i;
>>
>> #pragma omp parallel num_threads(m)
>> {
>> int just_to_make_some_code_generated;
>> just_to_make_some_code_generated = 0;
>> }
>> #pragma omp parallel for num_threads(n)
>> for(i = 0; i < 1; i++) {}
>>
>> }
>>
>> return 0;
>> }
>>
>> ---------------
>>
>> on FreeBSD6/7 (i386 and amd64) built with gcc42 or gcc43 -fopenmp (I have
>> not
>> tried other gcc versions), the memory usage is constantly growing during the
>> run. The memory growth is observed in case n != m. If n == m, everything
>> works
>> ok.
MG> The problem is observed also for constructions like this one:
MG> #pragma omp parallel for num_threads(m)
MG> ...
MG> #pragma omp parallel for num_threads(n)
MG> ...
MG> Adding some sleep() code I see in top that during the program run m or n
MG> threads are run in turn. So it looks like memory leaks when thread is
MG> removed. It might be FreeBSD problem, not gcc.
The problem is in libgomp/team.c. gomp_thread_start() does gomp_sem_init()
but gomp_sem_destroy() is never called. FreeBSD implementation of sem_init()
allocates some memory for semaphore. This patch solves the problem for me:
--- gcc-4.4-20090227/libgomp/team.c.orig 2009-05-16 22:57:05.000000000
+0300
+++ gcc-4.4-20090227/libgomp/team.c 2009-05-16 22:57:14.000000000 +0300
@@ -458,6 +458,7 @@ gomp_team_start (void (*fn) (void *), vo
void
gomp_team_end (void)
{
+ int i;
struct gomp_thread *thr = gomp_thread ();
struct gomp_team *team = thr->ts.team;
@@ -493,6 +494,9 @@ gomp_team_end (void)
}
while (ws != NULL);
}
+
+ for(i = 1; i < team->nthreads; i++)
+ gomp_sem_destroy (team->ordered_release[i]);
gomp_sem_destroy (&team->master_release);
#ifndef HAVE_SYNC_BUILTINS
gomp_mutex_destroy (&team->work_share_list_free_lock);
I am going to register this in bugzilla.
The problem is not observed under Linux, because it looks like sem_init()
implementation for Linux does not do memory allocation in the process' virtual
space. The memory for the test program below grows under FreeBSD and does not
under Linux.
#include <semaphore.h>
int
main(int argc, char *argv[]) {
sem_t sem;
for(;;) { sem_init(&sem, 0, 0);}
return 0;
}
--
Mikolaj Golub
