Monitorovani IO

kolik CPU/RAM zere jaky proces se zjisti snadno, napriklad vypisem iotop
monitorovani IO je zlozitejsi a dost casto zpomaluje system nejvic

existuji programy:
- iotop
- atop
- pidstat
- dstat (–topio, –topbio)
- vmstat (-d)
- iostat
- iozone
- sar

UseCase1

Here’s how you use it. First, get it:

wget http://aspersa.googlecode.com/svn/trunk/iodump

Then turn on kernel messages about I/O:

echo 1 > /proc/sys/vm/block_dump

This makes the kernel start writing messages about every I/O operation that takes place. Now all you have to do is get those messages and feed them into my script:

while true; do sleep 1; dmesg -c; done | perl iodump

Wait a little while, then cancel the script. The results should look something like the following:

root@kanga:~# while true; do sleep 1; dmesg -c; done | perl iodump
^C# Caught SIGINT.
TASK                   PID      TOTAL       READ      WRITE      DIRTY DEVICES
firefox               4450       4538        251       4287          0 sda4, sda3
kjournald             2100        551          0        551          0 sda4
firefox              28452        185        185          0          0 sda4
kjournald              782         59          0         59          0 sda3
pdflush                 31         30          0         30          0 sda4, sda3
syslogd               2485          2          0          2          0 sda3
firefox              28414          2          2          0          0 sda4, sda3
firefox              28413          1          1          0          0 sda4
firefox              28410          1          1          0          0 sda4
firefox              28307          1          1          0          0 sda4
firefox              28451          1          1          0          0 sda4

I deliberately generated a bunch of I/O by deleting my Firefox history and cache.

Do dmseq se zapisuje neco jako….

firefox(4450): WRITE block 25058328 on sda4
firefox(4450): WRITE block 25058336 on sda4
firefox(4450): WRITE block 25059104 on sda4

UseCase2

A quick way is to look at the /proc/[PID]/io file.

Example:

$ cat /proc/1944/io
read_bytes: 17961091072
write_bytes: 8192000
cancelled_write_bytes: 32768