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#if HAVE_CONFIG_H
# include "config.h"
#endif
/* $Id: shmtest.c,v 1.6 2003-10-22 22:12:21 d3h325 Exp $ */
#if HAVE_SYS_TYPES_H
# include <sys/types.h>
#endif
#if HAVE_SYS_IPC_H
# include <sys/ipc.h>
#endif
#if HAVE_SYS_SHM_H
# include <sys/shm.h>
#endif
#if HAVE_SYS_PARAM_H
# include <sys/param.h>
#endif
#if HAVE_ERRNO_H
# include <errno.h>
#endif
#if HAVE_STDIO_H
# include <stdio.h>
#endif
int armci_test_allocate(long size)
{
char *ptr;
long id = (long)shmget(IPC_PRIVATE, (size_t) size, (int)(IPC_CREAT | 00600));
if (id < 0L) {
return 0;
}
#if 0
/* attach to segment */
ptr = shmat((int) id, (char *) NULL, 0);
#else
ptr = (char *) NULL;
#endif
/* delete segment id */
if (shmctl((int) id, IPC_RMID, (struct shmid_ds *)NULL)) {
fprintf(stderr, "failed to remove shm id=%ld\n", id);
}
/* test pointer */
if (((long)ptr) == -1L) {
return 0;
}
else {
return 1;
}
}
/* parameters that define range and granularity of search for shm segment size
* UBOUND is chosen to be < 2GB to avoid overflowing on 32-bit systems
* smaller PAGE gives more accurate results but with more search steps
* LBOUND is set to amount that is considered insufficient for our purposes
*/
#define PAGE 131072L
#define UBOUND 2*4096*PAGE
#define LBOUND 4*PAGE
int verbose = 1;
/*\ determine the max shmem segment size using bisection
\*/
void armci_shmem_init()
{
long x, i, y = 0L;
long upper_bound = UBOUND;
long lower_bound = 0;
x = upper_bound;
for (i = 1;; i++) {
long step;
int rc = armci_test_allocate(x);
if (rc) {
if (verbose) {
printf("test %ld size=%ld bytes: success\n", i, x);
}
y = lower_bound = x;
step = (upper_bound - x) >> 1;
if (step < 16 * PAGE) {
break;
}
x += step;
}
else {
if (verbose) {
printf("test %ld size=%ld bytes: failed\n", i, x);
}
upper_bound = x;
step = (x - lower_bound) >> 1;
if (step < PAGE || x < LBOUND) {
break;
}
x -= step;
}
}
if (verbose) {
if (x < LBOUND) {
printf("no usable amount (%ld bytes) of shared memory available\n", LBOUND);
}
else {
printf("%ld bytes segment size, %ld calls \n", y, i);
}
}
else {
printf("%ld\n", y);
}
}
int main(int argc, char **argv)
{
if (argc > 1) {
verbose = 0;
}
if (verbose) {
printf("Searching for max shared memory segment size (SHMMAX) using bisection\n");
}
armci_shmem_init();
return 0;
}
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