Sunday, 8 April 2012

How-to: Stop Worrying about Duplicate Threads

I looked on my System Monitor recently and saw a lot of process with the same name and the same use of memory.

In particular:
  • ext4-dio-unwrit: 7 process
  • getty : 5 process
  • udevd : 3 process
  • gnome_keyring_daemon : 2 process
I never noticed these before. Are they all normal ? All the 'duplicates' belong to the same user.

However, we should not call those processes duplicated; they all have their own unique Process-ID (PID), so these processes all their own purpose and serve their own tasks.

The ext4-dio-unwrit processes, for example, are all set-up as rescuer threads to mop up any disk writes before the partitions are unmounted - there are seven because I have seven partitions in my filesystem. This is normal; the workqueues are created statically at mount time, one per cpu per file system.

A little research with a couple of utilities gave some reassurance that the others had unique purposes. We'll look at those another time. RC