Stress testing memory using malloc in linux ?? Post: 302380168

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Top Forums Programming Stress testing memory using malloc in linux ?? Post 302380168 by Corona688 on Monday 14th of December 2009 12:22:59 PM

12-14-2009

Registered User

Quote:

Originally Posted by frozensmilz

Hi to all,

Recently i am testing an equipment that runs in i586 fedora linux. I have to test mmap function. For that i determined to fill the memory and run the required application to check whether it throws any mmap error regarding low resources.

This is the line that does the allocation.
p = (long double *) malloc(BUFFSIZE);

In windows process explorer i have noticed that what ever value we give it to BUFFSIZE it will increase the size of "Private Bytes" but not working set memory or actual memory. In linux the memory still remains the same even after allocating about 1000MB.

Linux will show memory that is malloced but never used in any way under its' virtual memory stat.

If you want the system to actually run out of memory, and not kill random processes to regain it, you may want to turn overcommit and oom-kill off on your linux system. With overcommit enabled, it will only allocate memory you actually use. I cannot predict the effects of this on a system completely lacking in swap memory however -- why does your system not have it? Was Windows tested under these conditions too?

Code:

echo 2 > /proc/sys/vm/overcommit_memory
echo 0 > /proc/sys/vm/oom-kill

These settings are not persistent. If you reboot the machine, they will be set back to default values. Which are frankly more stable for reasons you're discovering -- it makes it harder for endless memory leaks to kill your machine. Not all versions of linux have /proc/sys/vm/oom-kill, I'm hunting for the alternative. You may find it listed by sysctl -A.

Quote:

The "memset" package is not available and cannot be installed

What memset package? If you mean the C function, it definitely has memset. You need to include <string.h>.

Last edited by Corona688; 12-14-2009 at 01:48 PM..

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LEARN ABOUT LINUX

malloc_stats

MALLOC_STATS(3) 					     Linux Programmer's Manual						   MALLOC_STATS(3)

NAME

       malloc_stats - print memory allocation statistics

SYNOPSIS

       #include <malloc.h>

       void malloc_stats(void);

DESCRIPTION

       The  malloc_stats()  function  prints  (on  standard error) statistics about memory allocated by malloc(3) and related functions.  For each
       arena (allocation area), this function prints the total amount of memory allocated and the total number of bytes consumed by in-use alloca-
       tions.	(These two values correspond to the arena and uordblks fields retrieved by mallinfo(3).)  In addition, the function prints the sum
       of these two statistics for all arenas, and the maximum number of blocks and bytes that were ever simultaneously allocated using mmap(2).

CONFORMING TO

       This function is a GNU extension.

NOTES

       More detailed information about memory allocations in the main arena can be obtained using mallinfo(3).

SEE ALSO

       mmap(2), mallinfo(3), malloc(3), malloc_info(3), mallopt(3)

Linux								    2012-05-06							   MALLOC_STATS(3)

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