Re: fastboot: unpacking initramfs faster

[Andreas Robinson <andr345@gmail.com>]

On Tue, 2009-03-24 at 23:11 +0100, Bodo Eggert wrote:
> Andreas Robinson <andr345@gmail.com> wrote:
> 
> > I tried running the initramfs unpacking asynchronously (and earlier) but
> > ran into a curious problem: The parent thread stalled until
> > decompression was done. I don't know why - I made sure that the two
> > threads ran on different cores. Perhaps the parent was cache starved.
> 
> I could not stall my system by gzip</dev/urandom>/dev/null.
> Maybe you accidentally used vfork?

No, this was an in-kernel test. I used the Arjan's new async facility
which calls kthread_create().

> > I then looked at multithreaded decompression and found that neither gzip
> > files nor deflate streams provide enough information (eg block lengths)
> > to let you share the decompression among threads.
> > 
> > It can be done of course, but obviously not without modifying file
> > formats and userspace tools.
> > 
> > (Thoughts of snowballs and hell presented themselves at this point.)
> 
> Why not make a new set? http://7eggert.dyndns.org:8080/l/bgz.tar.gz

Hmm, well if you think there is a chance of it being accepted, then
sure! I'll cook something up, but will be looking to use LZO first since
it's a bit faster to begin with.