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ep:labs:05:contents:tasks:ex1 [2019/10/27 17:10] emilian.radoi created |
ep:labs:05:contents:tasks:ex1 [2026/03/30 22:15] (current) radu.mantu |
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| - | ==== 01. [20p] Gnuplot graphs ==== | + | ==== 01. [20p] iostat & iotop ==== |
| - | + | ||
| - | Using the Gnuplot documentation, implement a script that plots four graphs. Use the data from {{:ep:laboratoare:data4.txt|}} as follows: the first graph should plot columns 1 and 2, the second columns 1 and 3, the third one columns 1 and 4, and the fourth one should be a 3D graph plotting columns 1, 2 and 3. | + | |
| - | * Use different colours for the data in each graph. | + | |
| - | * Remove the keys for each graph. | + | |
| - | * Give a title to each graph. | + | |
| - | * Give names to each of the axes: X or Y (or Z for the 3D graph). In the case of the 3D graph: Make the numbers on the axes readable, and correct the position of the names of the axes if these are displayed over the axes numbers. | + | |
| - | * Make the script generate the .eps file containing your plot. | + | |
| + | === [10p] Task A - Monitoring the behaviour with Iostat === | ||
| <note tip> | <note tip> | ||
| - | **Hint:** Consider the following commands: set key, xlabel, set title, set xtics, set terminal, set output, using. | + | Parameteres for iostat: |
| + | * -x for extended statistics | ||
| + | * -d to display device stastistics only | ||
| + | * -m for displaying r/w in MB/s | ||
| + | <code bash> | ||
| + | $ iostat -xdm | ||
| + | </code> | ||
| + | Use iostat with -p for specific device statistics: | ||
| + | <code bash> | ||
| + | $ iostat -xdm -p sda | ||
| + | </code> | ||
| </note> | </note> | ||
| + | |||
| + | * Run //iostat -x 1 5//. | ||
| + | * Considering the last two outputs provided by the previous command, calculate **the efficiency of IOPS** for each of them. Does the amount of data written per I/O **increase** or **decrease**? | ||
| + | |||
| + | Add in your archive screenshot or pictures of the operations and the result you obtained, also showing the output of iostat from which you took the values. | ||
| + | |||
| + | <note> | ||
| + | How to do: | ||
| + | |||
| + | * Divide the kilobytes read (//rkB/s//) and written (//wkB/s//) per second by the reads per second (//r/s//) and the writes per second (//w/s//). | ||
| + | * If you happen to have quite a few [[https://en.wikipedia.org/wiki/Loop_device|loop devices]] in your **iostat** output, find out what they are exactly: | ||
| + | |||
| + | <code bash> | ||
| + | $ df -kh /dev/loop* | ||
| + | </code> | ||
| + | </note> | ||
| + | |||
| <solution -hidden> | <solution -hidden> | ||
| - | <code> | + | The way to calculate the efficiency of IOPS is to divide the reads per second //(r/s)// and writes per second //(w/s)// by the kilobytes read //(rkB/s)// and written //(wkB/s)// per second. |
| - | reset #flush all variables | + | Example: the amount of data written per I/O for ///dev/sda// increases during each iteration: |
| - | set term postscript color eps enhanced | + | {{ :ep:labs:ep2017_l3_ex01.png?700 |}} |
| - | set output 'myplot.eps' | + | |
| - | set size 1,1 #use default pallet size(100% of width and height) | + | |
| - | set multiplot | + | |
| - | unset key | + | |
| - | #Graph 1 | + | <code> |
| - | set size 0.5,0.5 #half the width and height | + | 53040/105 = 505KB per I/O |
| - | set origin 0,0.5 #x,y | + | 71152/102 = 697KB per I/O |
| - | set title 'First' | + | </code> |
| - | plot 'data4.txt' using 1:2 w l lw 0.5 | + | |
| - | #Graph 2 | + | If everything is zero in iostat - perform some I/O operations... |
| - | set size 0.5,0.5 | + | </solution> |
| - | set origin 0.5,0.5 | + | |
| - | set xlabel 'X' | + | |
| - | set ylabel 'Y' | + | |
| - | set title 'Second' | + | |
| - | plot 'data4.txt' using 1:3 w l lw 0.5 | + | |
| - | #Graph 3 | ||
| - | set size 0.5,0.5 | ||
| - | set origin 0,0 | ||
| - | set xlabel 'X' | ||
| - | set ylabel 'Y' | ||
| - | set title 'Third' | ||
| - | plot 'data4.txt' using 1:4 w l lw 0.5 | ||
| - | #Graph 4 | + | === [10p] Task B - Monitoring the behaviour with Iotop === |
| - | set size 0.5,0.5 | + | <note tip> |
| - | set origin 0.5,0 | + | **Iotop** is an utility similar to top command, that interfaces with the kernel to provide per-thread/process I/O usage statistics. |
| - | set view 60,15 | + | |
| - | set xtics 0,1000 | + | |
| - | set ytics 1.8,0.3 | + | |
| - | set ztics 1,0.2 | + | |
| - | set xlabel 'X' offset 0,-1 | + | |
| - | set ylabel 'Y' | + | |
| - | set zlabel 'Z' | + | |
| - | set title 'Fourth' | + | |
| - | splot 'data4.txt' using 1:2:3 w l lw 0.5 lc rgb 'black' | + | |
| - | set xtics auto | + | |
| - | set ytics auto | + | |
| - | set ztics auto | + | |
| - | unset multiplot | + | <code> |
| + | Debian/Ubuntu Linux install iotop | ||
| + | $ sudo apt-get install iotop | ||
| + | How to use iotop command | ||
| + | $ sudo iotop OR $ iotop | ||
| </code> | </code> | ||
| + | |||
| + | Supported options by iotop command: | ||
| + | |||
| + | | **Options** | **Description** ^^ | ||
| + | | --version | show program’s version number and exit || | ||
| + | | -h, --help | show this help message and exit || | ||
| + | | -o, --only | only show processes or threads actually doing I/O || | ||
| + | | -b, --batch | non-interactive mode || | ||
| + | | -n NUM, --iter=NUM | number of iterations before ending [infinite] || | ||
| + | | -d SEC, --delay=SEC | delay between iterations [1 second] || | ||
| + | | -p PID, --pid=PID | processes/threads to monitor [all] || | ||
| + | | -u USER, --user=USER | users to monitor [all] || | ||
| + | | -P, --processes | only show processes, not all threads || | ||
| + | | -a, --accumulated | show accumulated I/O instead of bandwidth || | ||
| + | | -k, --kilobytes | use kilobytes instead of a human friendly unit || | ||
| + | | -t, --time | add a timestamp on each line (implies –batch) || | ||
| + | | -q, --quiet | suppress some lines of header (implies –batch) || | ||
| + | </note> | ||
| + | |||
| + | |||
| + | * Run iotop (install it if you do not already have it) in a separate shell showing only processes or threads actually doing I/O. | ||
| + | * Inspect the script code ({{:ep:laboratoare:dummy.sh|dummy.sh}}) to see what it does. | ||
| + | * Monitor the behaviour of the system with iotop while running the script. | ||
| + | * Identify the PID and PPID of the process running the dummy script and kill the process using command line from another shell (sending SIGINT signal to both parent & child processes). | ||
| + | * Hint - [[https://superuser.com/questions/150117/how-to-get-parent-pid-of-a-given-process-in-gnu-linux-from-command-line|How to get parent PID of a given process in GNU/Linux from command line?]] | ||
| + | |||
| + | <solution -hidden> | ||
| + | {{:ep:laboratoare:lab3-ex4.png?600}} | ||
| + | |||
| + | **dd** performs disk writes... wow! Reason why there are no disk reads is because it uses pseudo-files from **devtmpfs** that don't record these statistics. Also, **tmpfs** are not disks :p | ||
| + | |||
| + | Find PPID from PID: ps -o ppid= -p PID | ||
| + | Send SIGINT signal: kill -SIGINT PID,PPID | ||
| </solution> | </solution> | ||
