Chris Mason <chris.mason@xxxxxxxxxx> wrote:
> > This has the appearance of some really bad IO or VM latency
> > problem. Unfixed and present in stable kernel versions going from
> > years ago all the way to v2.6.36.
>
> Hmmm, the workload you're describing here has two special parts.
> First it dramatically overloads the disk, and then it has guis doing
> things waiting for the disk.
I think I see this same issue every few days when I back up my hard
drive to a USB hard drive using rsync. While the backup is running, the
interactive response is bad. A reproducible measurement of the badness
is starting an rxvt with F8 (bound to "rxvt &" in my .twmrc). Often it
takes 8 seconds for the window to appear (as it just did about 2 minutes
ago)! (Starting a subsequent rxvt is quick.)
The command for running the backup:
rsync -av --delete /etc /home /media/usbdrive/bak > /tmp/homebackup.log
The hardware is a T60 w/ Intel graphics and wireless, 1.5GB RAM, 5400rpm
160GB harddrive w/ ext3 filesystems, and it's running vanilla 2.6.36.
There's not much memory pressure. The swap is mostly empty, and there's
usually a Firefox eating 500MB of RAM. Even Emacs at 50MB is in the
noise compared to the Firefox.
Here's the 'free' output:
total used free shared buffers cached
Mem: 1545292 1500288 45004 0 92848 713988
-/+ buffers/cache: 693452 851840
Swap: 2000088 22680 1977408
What tests or probes are worth running when the problem reappears in
order to find the root cause?
-Sanjoy
`Until lions have their historians, tales of the hunt shall always
glorify the hunters.' --African Proverb
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