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Friday, October 04, 2013

Number of threads per state

awk with ps creates powerful Linux combo. For example there is one, or more, multi-threaded application on your system. You would like to know what states all those threads are. Standard ps show information about processes, but you can learn more about threads with "-L" switch. You probably hit another issue - number of threads, you don't want to analyse, let say, 300 lines. Lucky, awk is very good for such tasks. Following 'one-liner' shows number of threads and processes per state (running, sleeping, uninterrupted sleep), every 5 seconds.
while [ 1 ];
    ps -Leo pid,state,args| \
     awk '{state[$2]++} \
      END{ for (j in state) {printf "%s - %d\n", j, state[j]}}';
    echo "---";
    sleep 5;
First line ensures that command runs forever. ps uses '-e' (all processes), '-L' (include threads), '-o' (user specify output). There are 3 lines in ps output: PID, state and command arguments. (These arguments are useful for my other commands. In this case you can leave only 'state', but you has to modify awk command). Next awk takes every line and counts each state using state array with argument equal to state representation (i.e.: S for sleep, D for uninterrupted sleep, R for running). At the end of execution it prints each argument with it value. After that script displays '---'  and waits 5 seconds.
Such output can be valuable extension to top command results. It shows instant changes to number of busy processes, which affects system load.