PT - OS performance Monitoring using VMSTAT
vmstat
process ---- Memory ---- swap ---- i/o ----- system ---- cpu
Process : r | b
Memory : spwd | spwd | free | buffer | cache
Swap : si | so
I/O: bi | bo
System : cs | us | sy
CPU : id |wt | st
Field | Meaning |
r | number of processes waiting for run time |
b | number of processes in uninterruptible sleep |
spwd | Virtual memory swapped out to disk |
spwd | Virtual memory swapped out to disk |
free | Amount of free memory |
si | Amount of memory swapped in from disk | |
so | Amount of memory swapped to disk | |
us | User CPU time | |
bi | Blocks received from a block device (blocks/s) | |
bo | Blocks sent to a block device | |
sy | System CPU time | |
id | CPU idle time |
- vmstat command output example
- vmstat 2 ( output every 2 second)
- Example to apply load on OS by executing i/o 30 times using apply_io_stress.sh file.
cat > apply_io_stress.sh <<EOL
#!/bin/bash
counter=1
while [ \$counter -le 30 ]
do
dd if=/dev/zero of=/tmp/test1.img bs=500M count=1 oflag=dsync
((counter++))
done
rm -f /tmp/test1.img
EOL
- Provide execute permission below.
chmod +x apply_io_stress.sh
srv1:~ # sh apply_io_stress.sh
^Z
[1]+ Stopped sh apply_io_stress.sh
srv1:~ #
- We can see after executing sh file number of r b process increases also I/O bi bo reading blocks and write block increase.
^Z
[1]+ Stopped sh apply_io_stress.sh
- Once stopping apply_io_stress.sh file processes and I/O value came back to normal.
vmstat -d 2
- vmstat -d 2 ( Disk output at every 2 seconds) Examples below.
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