Dec 042011


IO wait load tracking to a process.

How to identify what processes are generating I/O wait load.

An easy way to identify what process is generating your IO Wait load is to enable block I/O debugging. This is done by setting /proc/sys/vm/block_dump to a non zero value like:

echo 1 > /proc/sys/vm/block_dump

This will cause messages like the following to start appearing in dmesg:

bash(6856): dirtied inode 19446664 ( on md1

Using the following one-liner will produce a summary output of the dmesg entries:

dmesg | egrep "READ|WRITE|dirtied" | egrep -o '([a-zA-Z]*)' | sort | uniq -c | sort -rn | head
354 md
324 export
288 kjournald
53 irqbalance
45 pdflush
14 portmap
14 bash
10 egrep
10 crond
8 ncftpput

Once you are finished you should disable block I/O debugging by setting /proc/sys/vm/block_dump to a zero value like:

echo 0 > /proc/sys/vm/block_dump



 Posted by at 9:14 am

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