Disk blocks for long periods

[Joakim Tjernlund]

> 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).

I am on PPC and SysRq-T does not display anything useful :-(
Perhaps readprofile?

> 
> >  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.

Perhaps kupdate is holding some VFS specific block? I am on a MV 2.4.2 kernel 

> 
> --
> dwmw2
> 
> 
>