Disk blocks for long periods

[David Woodhouse]

joakim.tjernlund at lumentis.se said:
>  I have noticed that if i copy a "big" file(580K) it sometimes take up
> to 42 seconds before it's finished. Normally it takes about 3-4
> seconds. When this long copy happen, top reports that kupdate and the
> copy(cp) process is in D state, the rest is sleeping. The FS is a 45%
> usage. FS is about 63MB in size. Using the stable branch.

> Why does it block for so long time?

Dunno. What's it doing? Where are cp and kupdate sleeping? (SysRq-T).

>  Also, if I fill the FS up to 100% and later reboots, it kan take
> 10-15 minutes before init starts to run. The root fs mount takes about
> 20 seconds and the system just stops between the last message from the
> kernel and when init prints its version.

> It is just the first reboot after I fill the FS, once I have gotten
> past the first reboot and reboots again, things are back to normal. 

More logs and SysRq-T required. Sounds like it's erasing blocks and for 
some reason not allowing anything else to happen while it's doing it.

--
dwmw2