displaying top cpu using process

displaying top cpu using process

[Dominik Vogt]

I want to have a button in the button bar of my window manager
(fvwm with FvwmButtons) that displays the process that currently
uses most CPU.  The information I want to display is the process
id, used CPU and the command line of the process, e.g.

  12345 99.0% netscape

The part dealing with X and the window manager is not the problen,
althoug it is not easy to do.  The problem is that it is
surprisingly difficult to get said information (SuSE 7.1 Linux
with 2.4.0 kernel)

I tried out about a dozen different programs that display load or
process information, and the only candidates I came across are ps
and top.

ps:

  ps gives me complete control over the output format, but I can't
  make it give me the CPU percentage.  Although the 'C' output
  modifier is documented as 

    "use raw CPU time for %CPU instead of decaying average"

  I always get the decaying average.  Because of this, most of the
  time I see that X uses most CPU.

top:

  Top provides all the output I need, but it is *very* cumbersome
  to parse.  Okay, I have an (inefficient) shell script that
  extracts the information:

    top -b -n 1 | sed '<script>'

  But then, this only works if the terminal window from which top
  was started has enough lines.  If its too short, top generates
  only the header or no lines at all.  This is certainly a strange
  notion of a batch mode (b option).  To get the full output I
  have to detach top from the terminal.  In other words, I need
  one process that generates the data and one that writes it into
  the terminal window.  There are several ways to do this, but
  the best solution seems to be a coprocess (because the coprocess
  is killed if the terminal window that runs the script is
  closed).

  Of course this all wastes a lot of cpu and memory and is very
  ugly to write.

Can anybody think of a better solution (that does not include
writing any C code)?

Bye

Dominik ^_^  ^_^

--
Dominik Vogt, dominik.vogt@gmx.de
Reply-To: dominik.vogt@gmx.de

Re: displaying top cpu using process

[Bart Schaefer]

On Apr 7,  4:33pm, Dominik Vogt wrote:
} Subject: displaying top cpu using process
}
}   ps gives me complete control over the output format, but I can't
}   make it give me the CPU percentage.  Although the 'C' output
}   modifier is documented as 
} 
}     "use raw CPU time for %CPU instead of decaying average"
} 
}   I always get the decaying average.

I can't even get my "ps" to accept the C modifier.  It keeps interpreting
it as the "selection by command name" option, and telling me that only
root is allowed to do that.

}     top -b -n 1 | sed '<script>'
} 
}   But then, this only works if the terminal window from which top
}   was started has enough lines. [...]  To get the full output I
}   have to detach top from the terminal.  

That's odd; on RH6.2, for me, "top -b -n 1" produces a lot more lines
of output than the height of the terminal.  (procps-2.0.6-5)  However,
try fooling it by stuffing the LINES and COLUMNS environment variables.

}   In other words, I need one process that generates the data and one
}   that writes it into the terminal window. There are several ways to
}   do this, but the best solution seems to be a coprocess (because the
}   coprocess is killed if the terminal window that runs the script is
}   closed).

A coprocess is overkill.  Just use the parameter assignment and a pipe:

topcpu {
  local p=0 pid user pri ni size rss share stat lib cpu mem time command
  LINES=10 COLUMNS=200 top d 2 c b n 43200 |
  while read pid user pri ni size rss share stat lib cpu mem time command
  do
    [[ $pid == PID ]] && { p=1; continue }
    (( p )) && { print $pid $cpu% $command; p=0 }
  done
}

43200 iterations of 2 sec is 24 hours.

} Can anybody think of a better solution (that does not include
} writing any C code)?

Presumably it's possible to compute the CPU percentages by reading from
/proc/<->/stat plus the cpu line from /proc/stat, but I don't know the
algorithm top uses.

-- 
Bart Schaefer                                 Brass Lantern Enterprises
http://www.well.com/user/barts              http://www.brasslantern.com

Zsh: http://www.zsh.org | PHPerl Project: http://phperl.sourceforge.net   

Re: displaying top cpu using process

[Dominik Vogt]

On Sat, Apr 07, 2001 at 06:26:01PM +0000, Bart Schaefer wrote:
> On Apr 7,  4:33pm, Dominik Vogt wrote:
> } Subject: displaying top cpu using process
> }
> }   ps gives me complete control over the output format, but I can't
> }   make it give me the CPU percentage.  Although the 'C' output
> }   modifier is documented as 
> } 
> }     "use raw CPU time for %CPU instead of decaying average"
> } 
> }   I always get the decaying average.
> 
> I can't even get my "ps" to accept the C modifier.  It keeps interpreting
> it as the "selection by command name" option, and telling me that only
> root is allowed to do that.

I remember that it was very difficult to make ps accept its
options, but it is possible.  The man page is really crap.  I
don't have the line handy right now, but I can look it up on
monday.

> }     top -b -n 1 | sed '<script>'
> } 
> }   But then, this only works if the terminal window from which top
> }   was started has enough lines. [...]  To get the full output I
> }   have to detach top from the terminal.  
> 
> That's odd; on RH6.2, for me, "top -b -n 1" produces a lot more lines
> of output than the height of the terminal.

Yes, it produces full output as long as the terminal window has at
least eight lines.  If the window is smaller, top only writes the
headers but no process information.

> (procps-2.0.6-5)  However,
> try fooling it by stuffing the LINES and COLUMNS environment variables.

Yes, that's it.  Setting LINES to a big value makes top produce
full output.  Now, how can I protect LINES from being reset when
the window is resized?

> }   In other words, I need one process that generates the data and one
> }   that writes it into the terminal window. There are several ways to
> }   do this, but the best solution seems to be a coprocess (because the
> }   coprocess is killed if the terminal window that runs the script is
> }   closed).
> 
> A coprocess is overkill.  Just use the parameter assignment and a pipe:

Yes, with a way to make top produce output in a 20x1 window a
background process is not necessary.

> topcpu {
>   local p=0 pid user pri ni size rss share stat lib cpu mem time command
>   LINES=10 COLUMNS=200 top d 2 c b n 43200 |
>   while read pid user pri ni size rss share stat lib cpu mem time command
>   do
>     [[ $pid == PID ]] && { p=1; continue }
>     (( p )) && { print $pid $cpu% $command; p=0 }
>   done
> }

Unfortunately the read command above will not work reliably which
complicates things a lot.  The number of space separated words in
the top output varies:

  354 luthien    8   0  2000 2000  1376 S     0.0  1.5   0:00 zsh
  525 luthien   13   5  1148 1148   932 S N   0.0  0.9   0:00 startx
                                        ^^^

> 43200 iterations of 2 sec is 24 hours.


My solution looks like this:

---------------------------------------------------------------
#!/usr/bin/zsh

emulate zsh
setopt EXTENDED_GLOB

function topcpu ()
{
  local p=0 pid rest
  LINES=10 COLUMNS=200 top -d 2 -c -b -s -n 1 |
  while read pid rest; do
    [[ $pid == PID ]] && { p=1; continue }
    (( p )) && {
      if [ ! $rest[57,60] = "top " ]; then
        print -n "\n"$pid ${rest[44,48]## ##}% ${rest[57,99]}
      fi
      return
    }
  done
}

topcpu
if [ -n $1 ]; then
  while true; do
    sleep $1 2> /dev/null
    topcpu
  done
fi
---------------------------------------------------------------

To circumvent the problem of the window being resized, the
function is called in a loop with a single pass of top each.
I call it from xterm:

  xterm -g 20x1 -font 5x7 +sb +aw +ah -e topproc 15

Unfortunately I can't make the cursor the same colour as the
window background.  Although xterm allows to set the colour, it
ignores the setting if it's identical to the background colour.
I guess I'll have to live with that (it *is* possible to solve,
even with the themes setup in fvwm, but it's not worth the
effort).

Bye

Dominik ^_^  ^_^

--
Dominik Vogt, dominik.vogt@gmx.de
Reply-To: dominik.vogt@gmx.de

Re: displaying top cpu using process

[Bart Schaefer]

On Apr 8,  2:49pm, Dominik Vogt wrote:
} Subject: Re: displaying top cpu using process
}
} >   LINES=10 COLUMNS=200 top d 2 c b n 43200 |
} >   while read pid user pri ni size rss share stat lib cpu mem time command
} 
}   525 luthien   13   5  1148 1148   932 S N   0.0  0.9   0:00 startx
}                                         ^^^

Urk, I forgot about that.  Your solution is probably the best for this
particular applicaton, but in case you actually want to parse it:

    ... | while read pid user pri ni size rss share stat rest
    do
	rest=($=rest)
	[[ $rest[1] == <->* ]] || { stat="$stat $rest[1]" ; shift rest }
	lib=$rest[1]	# Your output does not have this item?  Renumber.
	cpu=$rest[2]
	mem=$rest[3]
	time=$rest[4]
	command=$rest[5,-1]
	...
    done

I don't think top ever produces more than 2 words in the STAT column,
does it?

-- 
Bart Schaefer                                 Brass Lantern Enterprises
http://www.well.com/user/barts              http://www.brasslantern.com

Zsh: http://www.zsh.org | PHPerl Project: http://phperl.sourceforge.net