Opinions on memory increase Post: 41057

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Top Forums UNIX for Advanced & Expert Users Opinions on memory increase Post 41057 by Perderabo on Sunday 28th of September 2003 09:53:09 PM

09-28-2003

Administrator Emeritus

This is lot more info than you originally posted. Still, I would use a phrase like "dipping our toe in" rather than "this deep".

If you are sure that you are swapping and not just paging, then there is no question. You will benefit from more memory. But this only applies to daytime load where you see the swapping activity.

Your nightly jobs which are cpu bound will not benefit very much from the additional memory. Since these are batch jobs that are run overnight, why worry about them? Are they in danger of not completing overnight?

100% cpu could just mean you are compute bound. Imagine a system with one cput that is lightly loaded. Now I add a single process that is finding very large prime numbers. You now have 100% cpu utilization. This is not a real big deal all by itself. The process will have its priority lowered to the minimum very quickly. It will run only when no other process wants the cpu.

Now replace the cpu with a super cpu. My program will now find very large primes faster, but the cpu is still at 100%

So you may not have a problem with your nightly batch jobs. It's rare to use a computer for computation, but it does happen.

Also, next year is just a few months away. I would really resist investing in a system that is being replaced that soon.

Perderabo

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LEARN ABOUT DEBIAN

sg_get_swap_stats

sg_get_mem_stats(3)					     Library Functions Manual					       sg_get_mem_stats(3)

NAME

       sg_get_mem_stats, sg_get_swap_stats - get VM statistics

SYNOPSIS

       #include <statgrab.h>

       sg_mem_stats *sg_get_mem_stats(void);

       sg_swap_stats *sg_get_swap_stats(void);

DESCRIPTION

       Memory statistics are accessed through the sg_get_mem_stats function. It returns a pointer to a static sg_mem_stats.

       The sg_get_swap_stats returns returns swap statistics. It returns a pointer to a static sg_swap_stats.

       On  the	FreeBSD  operating system elevated privileges are required to access the swap statistics. Making the program setgid kmem should be
       sufficient. Programs running as root will not have this problem.

RETURN VALUES

       The VM system calls can return a pointer to either a sg_mem_stats or a sg_swap_stats.

       typedef struct{
	       long long total;
	       long long free;
	       long long used;
	       long long cache;
       }sg_mem_stats;

       total  The total amount of memory in bytes.

       free   The total free memory in bytes.

       used   The total used memory in bytes.

       cache  The amount of cache used in bytes.

       typedef struct{
	       long long total;
	       long long used;
	       long long free;
       }sg_swap_stats;

       total  The total swap space in bytes.

       used   The used swap in bytes.

       free   The free swap in bytes.

TODO

       Add a function to hold open the file descriptor to the kernel memory structures. Doing this would  allow  the  elevated	privileges  to	be
       dropped early on.

SEE ALSO

       statgrab(3)

WEBSITE

       http://www.i-scream.org/libstatgrab/

i-scream						   $Date: 2005/04/25 11:25:45 $ 				       sg_get_mem_stats(3)