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root/i-scream/projects/libstatgrab/docs/cpu.txt
Revision: 1.1
Committed: Sun Aug 24 21:00:32 2003 UTC (21 years, 2 months ago) by pajs
Content type: text/plain
Branch: MAIN
Log Message:
CPU documentaion

File Contents

# User Rev Content
1 pajs 1.1 CPU Statistics
2    
3     cpu_states_t *get_cpu_totals();
4     cpu_states_t *get_cpu_diff();
5     cpu_percent_t *cpu_percent_usage();
6    
7     typedef struct{
8     long long user;
9     long long kernel;
10     long long idle;
11     long long iowait;
12     long long swap;
13     long long nice;
14     long long total;
15     time_t systime;
16     }cpu_states_t;
17    
18     typedef struct{
19     float user;
20     float kernel;
21     float idle;
22     float iowait;
23     float swap;
24     float nice;
25     time_t time_taken;
26     }cpu_percent_t;
27    
28     get_cpu_totals() and get_cpu_diff() both return static pointers of
29     type cpu_states_t. get_cpu_totals() returns the total amount of "ticks"
30     the OS has spent in each of the different states. get_cpu_diff() returns
31     the difference in "ticks" for each of the states since last time get_cpu_diff()
32     or get_cpu_totals() was called. If it has never been called, it will return
33     the result of get_cpu_totals()
34    
35     The vaule stored (the "ticks") will vary from OS to OS. E.g. solaris has a
36     total of 100 per second. Linux has substatially more than that. Also, different
37     OS's store different information. E.g. solaris doesn't do nice.
38    
39     Because of this, ideally you will always want to work on a scale against the
40     total, or in percentages.
41    
42     cpu_percent_usage() returns a pointer to a static cpu_percent_t. The function calls
43     get_cpu_diff() and changes the values into percentages. If its never been called
44     before (and nor has get_cpu_totals() and get_cpu_diff() ), the returned percentages
45     will be the systems total ever since its uptime. (Unless the counters of cycled)