Since you are running 11.31 (required for the i6 blade you are using), compiling the program as a 64bit program removes any restrictions from the program and are limited by MAXDSIZ_64bit. NOTE: MAXDSIZ_64bit must be larger than MAXDSIZ. If MAXDSIZE_64bit = 1GB, then setting MAXDSIZ to 2GB has no effect -- both will limit data areas to 1GB.
Below is code for mallocmegs which can demonstrate all the compile options.
Start by setting MAXDSIZ to 3GB and MAXDSIZ_64bit to 32GB or larger. These are only runaway programming limits and have no effect on smaller programs.
kctune maxdsiz=3000000000
kctune maxdsiz_64bit=32000000000
Here's the program. Comments show how to compile it for different memory limits.
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
/*
Program to request megs of RAM to demo malloc
=============================================
Compile with no flags to allow up to 900 megs.
cc -Ae -o mallocmegs mallocmegs.c
Compile with -N to allow up to 1700 megs.
cc -Ae -N -o mallocmegs mallocmegs.c
Use "chatr +q3p enable" to increase to about 2700 megs:
chatr +q3p enable mallocmegs
and chatr +q4p enable mallocmegs to reach 3700 megs.
+q4p = enable mallocmegs
For 11.23 (and later), the MPAS address model is available for
32bit programs. Use the option:
-Wl,+as,mpas
and the result is an executable with 3800 meg capability
with no chatr needed and less restrictions on quadrant maps.
Compile with +DA2.0W or +DD64 to create a 64bit program.
With a 64-bit program, only maxdsiz_64 (and swap) limits
the total malloc area.
==============================
There can be problems with applying chatr +q3p and +q4p to some programs. A
program that has +q3p enabled cannot map shared memory segments that were
created by other processes in the third quadrant. A program using +q3p and
+q4p cannot map any shared memory segments created by other processes.
Code compiled with +Oaggressive will have +Osignedpointers assumptions in
the generated code. That can cause bad pointer comparisons between addresses
in the first two and the last two quadrants. +q3p makes that kind of pointer
comparison more likely.
*/
int main()
{
extern int errno;
int strerror_r(int errnum, char *buffer, int buflen);
#define l_BUFLEN_MAX 80
int nmeg,l_retval,l_errno,tot_megs;
void *mptr;
char *ptr,buf[128],l_errbuf[l_BUFLEN_MAX];
char *t;
int n;
tot_megs=0;
while (1) {
printf("Additional megs to malloc or CTRL-D: ");
ptr=fgets(buf,20,stdin);
if (ptr==NULL)
{
printf("\n\n");
exit (0);
}
n=atoi(buf);
nmeg=n*(1024*1024);
tot_megs=(tot_megs+n);
/* clear errno before our call */
errno = 0;
/* local errbuf is set to zero-length string */
l_errbuf[0]=NULL;
/* let's try to get some more memory */
mptr=malloc(nmeg);
/* capture errno before another call changes it */
l_errno = errno;
if (mptr == NULL)
{
/* simple error message */
printf("malloc %d more megs failed (%d total)\n",n,tot_megs);
sprintf(l_errbuf,
"errno %d from malloc getting %d megs more memory",l_errno,n)
;
perror(l_errbuf);
exit(1);
}
else
{
printf("Got %d megs more RAM, %d megs total\n\n",n,tot_megs);
}
/* put ! chars in the array to make it occupy real RAM */
for (n=0;n<nmeg;n+=1024)
{
*((char *)mptr+n)='!';
}
} /* while */
printf("\n\n");
return 0;
} /* main */
Bill Hassell, sysadmin
