Noam Bernstein <noam.bernst...@nrl.navy.mil> writes: > Can anyone shed some light on where the _virtual_ memory limit comes from?
Perhaps it comes from a VSizeFactor setting in slurm.conf:
VSizeFactor
Memory specifications in job requests apply to real memory size
(also known as
resident set size). It is possible to enforce virtual memory
limits for both
jobs and job steps by limiting their virtual memory to some
percentage of
their real memory allocation. The VSizeFactor parameter specifies
the job's or
job step's virtual memory limit as a percentage of its real
memory limit. For
example, if a job's real memory limit is 500MB and VSizeFactor is
set to 101
then the job will be killed if its real memory exceeds 500MB
or its virtual
memory exceeds 505MB (101 percent of the real memory limit).
The default
value is 0, which disables enforcement of virtual memory
limits. The value
may not exceed 65533 percent.
> 1. If I define DefMemPerCPU in the partition line, and the job doesn't request
> anything else, what memory measure should expect this to be the limit
> on? RSS?
Yes, RSS.
To test our memory settings, we often use a small program like the
attached C program. It first allocates memory (to test vmem limit),
then fills it with values (to test rss limit), and finally re-reads the
memory (to check for swapping).
It is built like this
gcc -DMB=$((30*1024)) -o malloc_30 malloc.c
for allocating 30 GiB. (Yes, I could have made the size a command line
parameter, but I am lazy. :)
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#define BYTES (MB * 1024 * 1024ul)
#define SEGMENT_SIZE 1024 /* num bytes to set at a time.
Must divide BYTES */
#define SLEEP 10
int main () {
char *large;
int single, read_size = sizeof(int);
unsigned long i;
large = (char *)malloc(BYTES*sizeof(char));
if (large != NULL) {
printf("Malloc: allocated %lu B\n", BYTES);
} else {
printf("Malloc: Aaargh! Crash and burn...\n");
exit(1);
}
fflush(NULL);
printf("Malloc: sleeping for %d seconds...\n", SLEEP);
fflush(NULL);
sleep(SLEEP);
printf("Malloc: Starting to fill...\n");
fflush(NULL);
for (i = 0; i < BYTES; i += SEGMENT_SIZE) {
memset(large + i, 42, SEGMENT_SIZE);
}
printf("Malloc: Filled %lu bytes\n", i);
fflush(NULL);
printf("Malloc: sleeping for %d seconds...\n", SLEEP);
fflush(NULL);
sleep(SLEEP);
printf("Malloc: Starting to read...\n");
fflush(NULL);
for (i = 0; i < BYTES; i += read_size) {
single = *(int*)(large + i);
//single = *(large + i);
}
printf("Malloc: Read %lu bytes\n", i);
fflush(NULL);
printf("Malloc: sleeping for %d seconds...\n", SLEEP);
fflush(NULL);
sleep(SLEEP);
printf("Malloc: done.\n");
fflush(NULL);
return 0;
}
-- Regards, Bjørn-Helge Mevik, dr. scient, Department for Research Computing, University of Oslo
signature.asc
Description: PGP signature
