[Bug 217815] Re: Installation stalls randomly until a key is pressed

[Matt Zimmerman]

On Mon, Apr 21, 2008 at 10:21:46AM -0000, Colin King wrote:
> A couple of points worth mulling over to corner this one..
> 
> 1. Is the "hanging" a function of memory size - for example, the buffer
> cache filling up after a certain amount of time and then pdflush kicking
> in very aggressively doing dirty data writing backs as fast as it can.
> In which case, one may see the system resume again after a (long) period
> of time once pdflush is complete.  It may be worth tweaking with the
> /proc/sys/vm/dirty* options to see if this trips the problem more
> frequently. Also, it may be worth seeing if doing the install with small
> memory kvm virtual machines shows this problem earlier than large memory
> virtual machines just to see if it is a buffer cache write back cpu
> starvation issue.
> 
> 2. From my understanding dd is being used to zero the encrypted disk.
> Does changing the dd block size to a very large size trip this bug
> earlier as one gets more throughput than the normal (small) block size
> default?

It's a custom program, actually, blockdev-wipe (in the partman-crypto
package).

> 3. Is the hanging resumed by an external interrupt (keyboard, mouse)
> because of the scheduler boosts interactive sessions temporarily and
> hence interfering (in a positive way) to the balancing of the encryption
> kernel space thread, dd and pdflush?

Note also that there are reports of similar behaviour in other parts of the
installer, which aren't necessarily as I/O intensive.

-- 
 - mdz

-- 
Installation stalls randomly until a key is pressed
https://bugs.launchpad.net/bugs/217815
You received this bug notification because you are a member of Ubuntu
Server Team, which is a direct subscriber.