portable implementation of load-average

portable implementation of load-average

[Joe Buehler]

My AIX 4.3 boxes did not support load average in the modeline
(emacs 21.2 if it matters) so I fixed it.

Looking at this, it appears to be because /dev/kmem needs to be read
for the information, and setting emacs setgid to group 0 would be a big
security hole.

Attached is a portable implementation in LISP that uses the
"uptime" program.  Please consider adding this to emacs.  You should
have a copyright assignment on file for me for emacs.

The "uptime" program provides compatible output
formats (and so the below works) on AIX 4.3, AIX 5.2, Solaris 8,
HPUX 11, HPUX 11i, RedHat 9 -- all the machines to which I have access.

I'm not a LISP programmer -- feel free to do whatever with
my implementation if you don't like it.
-- 
Joe Buehler

;; supply a portable definition of load-average if the emacs one does not work
(condition-case nil
	(load-average)
   (error
    (defun load-average (&optional wantfloat)
	 "get load average"
	 (let ((uptime (shell-command-to-string "/usr/bin/uptime")))
	   (if (string-match "load average: \\([0-9.]+\\), \\([0-9.]+\\), \\([0-9.]+\\)" uptime)
		   (if wantfloat
			   (list
				(string-to-number (match-string 1 uptime))
				(string-to-number (match-string 2 uptime))
				(string-to-number (match-string 3 uptime))
				)
			 (list
			  (truncate (* 100 (string-to-number (match-string 1 uptime))))
			  (truncate (* 100 (string-to-number (match-string 2 uptime))))
			  (truncate (* 100 (string-to-number (match-string 3 uptime))))
			  )
			 )
		 (if wantfloat
			 (list 0.0 0.0 0.0)
		   (list 0 0 0)
		   )
		 )
	   )
	 )
    ))

;;;;;; the end

Re: portable implementation of load-average

[Stefan Monnier]

> 	 (let ((uptime (shell-command-to-string "/usr/bin/uptime")))

You probably want to use `call-process' here instead, so as to avoid running
`sh' (running `uptime' is already making your `load-average' much slower
than the C version, so I think it's important to try and limit the inflicted
pain).

Maybe caching, so as to only run `uptime' at most once every minute or so,
would be in order.

BTW, is /usr/bin/uptime setgid 0 on those systems, or does it use some other
method to get the info (a method that Emacs could maybe use)?

> 	   (if (string-match "load average: \\([0-9.]+\\), \\([0-9.]+\\), \\([0-9.]+\\)" uptime)
> 		   (if wantfloat
> 			   (list
> 				(string-to-number (match-string 1 uptime))
> 				(string-to-number (match-string 2 uptime))
> 				(string-to-number (match-string 3 uptime))
> 				)
> 			 (list
> 			  (truncate (* 100 (string-to-number (match-string 1 uptime))))
> 			  (truncate (* 100 (string-to-number (match-string 2 uptime))))
> 			  (truncate (* 100 (string-to-number (match-string 3 uptime))))
> 			  )
> 			 )
> 		 (if wantfloat
> 			 (list 0.0 0.0 0.0)
> 		   (list 0 0 0)
> 		   )
> 		 )

How 'bout:

  (mapcar (if wantfloat 'identity (lambda (x) (truncate (* 100 x))))
          (if (string-match "load average: \\([0-9.]+\\), \\([0-9.]+\\), \\([0-9.]+\\)" uptime)
	      (mapcar (lambda (n) (string-to-number (match-string n uptime)))
                      '(1 2 3))
            '(0.0 0.0 0.0)))


-- Stefan

Re: portable implementation of load-average

[Joe Buehler]

Stefan Monnier wrote:

> You probably want to use `call-process' here instead, so as to avoid running
> `sh' (running `uptime' is already making your `load-average' much slower
> than the C version, so I think it's important to try and limit the inflicted
> pain).

Like I said, I'm not a LISP programmer -- it's all yours, feel free to
change what you want.

The only way I currently use it is as part of (display-time), so I don't
need any caching myself -- it runs once a minute as is.

> BTW, is /usr/bin/uptime setgid 0 on those systems, or does it use some other
> method to get the info (a method that Emacs could maybe use)?

It is not setgid for linux and solaris, it is setgid for the others.  Whether emacs
works as is for linux and solaris I don't know, but I presume it does not
work for the other OS's -- definitely not for AIX 4.3.
-- 
Joe Buehler