Re: Capturing load average from within systemtap script...

[Rick Beldin <rick dot beldin at hp dot com>]

Hi Eugene... 

	Thanks for the feedback. 

On Thu, 2008-02-07 at 11:54 +0000, Eugene Teo wrote:
> Hi Rick,
> 
> <quote sender="Rick Beldin">
> > I've been struggling for a bit on how to (or if possible) to capture the
> > value of avenrun (declared as:
> >
> > unsigned long avenrun[3];
> > EXPORT_SYMBOL(avenrun);
> [...]
> 
> > global timer_count
> 
> %{
> #include <linux/sysrq.h>
> 
> /* defined in fs/proc/proc_misc.c */
> #define LOAD_INT(x) ((x) >> FSHIFT)
> #define LOAD_FRAC(x) LOAD_INT(((x) & (FIXED_1-1)) * 100)
> %}
> 
	Ok.  This will be helpful. 

> > function rab_show_mem:long (arg:long)
> > %{
> >         handle_sysrq('m', NULL, NULL);
> >         handle_sysrq('t', NULL, NULL);
> 
> void handle_sysrq(int key, struct tty_struct *tty);
> 
> So, it should be handle_sysrq('m', NULL);
> 
	It looks like it changed in later kernels.  Thanks.  The
	environment I deal with typically limits me to production
	kernels from Red Hat and Novell.   For example, both 
	RHEL4's 2.6.9 and RHEL5's 2.6.18 kernels still have handle_sysrq
	defined this way: 

void handle_sysrq(int, struct pt_regs *, struct tty_struct *);

	I guess I'll have to put some ifdef's for other kernels or 
	keep very close track of this. 

> > %}
> > probe timer.ms(3000) {
> >     if (timer_count < 5) {
> >         printf("timer %d %d\n", rab_show_mem(0),timer_count++)
> >         ave = kernel_long(avenrun)
> >         printf("avenrun %d\n",ave)
> 
> function get_avenrun:string (idx:long) %{ /* pure */
>         if (THIS->idx < 0 || THIS->idx > 2)
>                 strcat(THIS->__retvalue, "0");
>         else {
>                 int a = avenrun[THIS->idx] + (FIXED_1/200);
>                 snprintf(THIS->__retvalue, MAXSTRINGLEN, "%d.%02d",
>                                 LOAD_INT(a), LOAD_FRAC(a));
>         }
> %}
> 
> in hangwatch.c, it reads the first value from /proc/loadavg, so in this case
> we are interested in avenrun[0]:
> 
	You are right. 

	Thanks.  I'll try to implement these ideas.   

	Rick 


-- 
+----------------------------------------------------------------------+
| Rick Beldin                    |  Hewlett-Packard Company            |
| email: Rick.Beldin@hp.com      |  Global Solutions Engineering       |
| WTEC Linux, RHCE               |  5555 Windward Parkway West         |
|                                |  Alpharetta, GA 30004               |
+----------------------------------------------------------------------+