Re: [LTP] [PATCH] cpuctl_fj: replace ps by top to fix cpu usage's computation error

[Jiri Palecek <jpalecek@web.de>]

On Wednesday 06 January 2010 10:47:34 Shi Weihua wrote:
> at 2010-1-6 13:24, Garrett Cooper wrote:
> > On Tue, Jan 5, 2010 at 8:58 PM, Shi Weihua <shiwh@cn.fujitsu.com> wrote:
> >> Some abnormal messages outputted in my x86_64.
> >> -------------------
> >> pid 4622 cpu_usage 0
> >> cpuctl_test_fj    1  TFAIL  :  case19    FAIL
> >> pid 4646 cpu_usage 0
> >> cpuctl_test_fj    1  TFAIL  :  case20    FAIL
> >> pid 4670 cpu_usage 63
> >> cpuctl_test_fj    1  TFAIL  :  case21    FAIL
> >> -------------------
> >> I think cpu usage's computation error occured.
> >> So I tried to use the oldest arithmetic of cpu usage, fortunately it works.
> >> Maybe we should replace 'ps' by 'top' in  get_cpu_usage().
> >> By the way, I increased the admissible range of cpu usage in case21()
> >> because it jumps out range of 44-56 sometimes.
> >>
> >> My patch works now:
> >> -------------------
> >> pid 20277 cpu_usage 97
> >> cpuctl_test_fj    1  TPASS  :  case19    PASS
> >> pid 20307 cpu_usage 99
> >> cpuctl_test_fj    1  TPASS  :  case20    PASS
> >> pid 20336 cpu_usage 55
> >> pid 20336 cpu_usage 53
> >> pid 20336 cpu_usage 55
> >> pid 20336 cpu_usage 57
> >> pid 20336 cpu_usage 55
> >> pid 20336 cpu_usage 55
> >> pid 20336 cpu_usage 55
> >> pid 20336 cpu_usage 55
> >> pid 20336 cpu_usage 57
> >> pid 20336 cpu_usage 53
> >> cpuctl_test_fj    1  TPASS  :  case21    PASS
> >> -------------------
> >>
> >> Signed-off-by: Shi Weihua <shiwh@cn.fujitsu.com>
> >> ---
> >> --- ltp-full-20091231/testcases/kernel/controllers/cpuctl_fj/run_cpuctl_test_fj.sh      2009-11-16 15:40:40.000000000 +0800
> >> +++ ltp-full-20091231.new/testcases/kernel/controllers/cpuctl_fj/run_cpuctl_test_fj.sh  2010-01-06 12:36:32.000000000 +0800
> >> @@ -85,7 +85,10 @@ creat_process()
> >>
> >>  get_cpu_usage()
> >>  {
> >> -       ps -eo 'pid,pcpu' | awk '$1 == "'$1'" { sub(/(\.[[:digit:]])*$/, "", $2); print $2 }'
> >> +       top=($(top -b -n 1 -p $1 | tail -2 | head -1))
> >> +       top=${top[8]}
> >> +       top=`echo $top | awk -F "." '{print $1}'`
> >> +       echo "$top"
> >>  }
> >>
> >>  kill_all_pid()
> >> @@ -627,7 +630,7 @@ case21()
> >>        do
> >>                cpu_usage=$(get_cpu_usage $pid)
> >>                echo "pid $pid cpu_usage $cpu_usage"
> >> -               expr 44 \< "$cpu_usage" \& "$cpu_usage" \< 56 > /dev/null 2>&1
> >> +               expr 40 \< "$cpu_usage" \& "$cpu_usage" \< 60 > /dev/null 2>&1
> >>                ret=$?
> >>                : $(( top_times+=1 ))
> >>        done
> > 
> >     Could you add a set -x to the top of the script so we can see the
> > output please? ps --version would be helpful too..
> 
> I wish it can help you.
> --------------------- sh -x -----------------------------
> + for i in '$(seq 1 $TST_TOTAL)'
> + setup

[ ... snip ... ]

I believe Garrett Cooper meant to send the trace output of the original script (the one with ps).

However, I'm not sure about the awk program there - particularly:

sub(/(\.[[:digit:]])*$/, "", $2)

should probably be

sub(/\.[[:digit:]]*$/, "", $2) 

(without the group). Not sure if this can actually cause what you see.

Also, I think we could simplify it a bit further, to something like this:

get_cpu_usage()
{
  ps -p $1 -o pcpu= | awk -F "." '{print $1}'
}

Please, tell me what do you think about it.

Regards
    Jiri Palecek

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