libstatgrab/docs/vm_stats.txt

VM Statistics
=============

$Id: vm_stats.txt,v 1.2 2003/08/24 20:24:08 tdb Exp $

Data Structures
---------------

These two structures can be returned by the VM system calls:

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

total   contains the total memory in bytes.
free    is the total free memory in bytes.
used    is the total used memory in bytes.
cache   is the cache used in bytes.

nb: Cache is not available on all operating systems (for example,
    Solaris). Free memory and cache memory can sometimes be linked.

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

total   contains the total swap space in bytes.
used    is the used swap in bytes.
free    is the free swap in bytes.

Functions
---------

mem_stat_t *get_memory_stats();

swap_stat_t *get_swap_stats();

Memory statistics are accessed through the first call. It returns
a pointer to a static mem_stat_t.

The second call returns swap statistics. It returns a pointer to
a static swap_stat_t.

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.

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.

Example
-------

An example can be found in examples/vm_stats.
Revision:	1.3
Committed:	Thu Oct 2 16:30:54 2003 UTC (22 years, 2 months ago) by tdb
Content type:	text/plain
Branch:	MAIN
CVS Tags:	HEAD
Changes since 1.2:	+1 -1 lines
State:	*FILE REMOVED*
Log Message:	Dropped the old text documentation in favour of manpages.
#	User	Rev	Content
1	tdb	1.2	VM Statistics
2			=============
3
4	tdb	1.3	$Id: vm_stats.txt,v 1.2 2003/08/24 20:24:08 tdb Exp $
5	tdb	1.2
6			Data Structures
7			---------------
8
9			These two structures can be returned by the VM system calls:
10	pajs	1.1
11			typedef struct{
12			long long total;
13			long long free;
14			long long used;
15			long long cache;
16			}mem_stat_t;
17
18	tdb	1.2	total contains the total memory in bytes.
19			free is the total free memory in bytes.
20			used is the total used memory in bytes.
21			cache is the cache used in bytes.
22	pajs	1.1
23	tdb	1.2	nb: Cache is not available on all operating systems (for example,
24			Solaris). Free memory and cache memory can sometimes be linked.
25	pajs	1.1
26			typedef struct{
27			long long total;
28			long long used;
29			long long free;
30			}swap_stat_t;
31
32	tdb	1.2	total contains the total swap space in bytes.
33			used is the used swap in bytes.
34			free is the free swap in bytes.
35
36			Functions
37			---------
38
39			mem_stat_t *get_memory_stats();
40
41			swap_stat_t *get_swap_stats();
42
43			Memory statistics are accessed through the first call. It returns
44			a pointer to a static mem_stat_t.
45
46			The second call returns swap statistics. It returns a pointer to
47			a static swap_stat_t.
48
49			On the FreeBSD operating system elevated privileges are required
50			to access the swap statistics. Making the program setgid kmem should
51			be sufficient. Programs running as root will not have this problem.
52
53			Todo
54			----
55
56			Add a function to hold open the file descriptor to the kernel memory
57			structures. Doing this would allow the elevated privileges to be
58			dropped early on.
59	pajs	1.1
60	tdb	1.2	Example
61			-------
62	pajs	1.1
63	tdb	1.2	An example can be found in examples/vm_stats.