Linux performance tuning:

https://www.linkedin.com/learning/linux-performance-tuning?trk=eml-email_learning_engagement_single_01-learning_recommendations-4-null&trkEmail=eml-email_learning_engagement_single_01-learning_recommendations-4-null-null-asylfx~jo4nf03y~ja-null-learning~course&lipi=urn%3Ali%3Apage%3Aemail_email_learning_engagement_single_01%3BZvLe9h85RFG5%2FUEcK7sbgw%3D%3D

 

A Time

 1. The time command in shell

/usr/bin/time <command>

 

Example1

/usr/bin/time sleep 2

Output1:

0.00user 0.00system 0:02.01elapsed 0%CPU (0avgtext+0avgdata 4944maxresident)k
0inputs+0outputs (0major+55minor)pagefaults 0swaps

 

Example2

#! /bin/bash
###loop.ah####
    x=$((x+1))
    /bin/pwd > /dev/null
    if [ $x -gt 5000 ]
    then
        exit
    fi
done

#########Run "time loop.sh" in bash####
bash-3.2$ time ./loop.sh

Output2:

real 0m8.698s
user 0m2.181s
sys 0m5.474s

 

2. time command in C

• gettimeof day()
• clock_gettime()

 

B. Operations per Second

C. The strace command

It can helps out check the time usage detail. (We can find the time of using '/bin/pwd' is much longer than using 'pwd'.

So when the type of command is "a shell builtin", we'd better use the command directly.

 strace -c -o  <files to save output>  <command>

####Example####
 strace -c -o /tmp/s.out ./loop.sh


##### check the output ###
 head -4 /tmp/s.out

output:

% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
31.41 0.093416 4 25007 fcntl
18.96 0.056396 4 15010 rt_sigprocmask