Re: [Qemu-devel] Question about qemu firmware configuration (fw_cfg) device

[Richard W.M. Jones]

On Mon, Jul 19, 2010 at 11:40:41AM +0300, Gleb Natapov wrote:
> On Mon, Jul 19, 2010 at 09:34:11AM +0100, Richard W.M. Jones wrote:
> > On Mon, Jul 19, 2010 at 10:55:33AM +0300, Gleb Natapov wrote:
> > > Why not put then on cdrom or disk?
> > 
> > It simplifies device and mountpoint enumeration not to have a separate
> > disk.  It would also mean we couldn't use standard Fedora paths, or
> > we'd have to have bind-mount /bin etc on to the disk mount point,
> > which again complicates things.
> > 
> Can't help you here, but if it's doable you can speedup your startup
> time much more then by a second.

This isn't true.

The most we could save is 0.8 seconds [time taken to load the 100MB
initrd by the kernel] less the time taken to probe and mount a CD ISO
[0.2 seconds - measured using guestfish] less the time taken to load
programs from this CD.  So the most we could save would be 0.6
seconds, and in reality it'd be less than this if we actually loaded
and ran any programs from the CD at all.

My patch saves 1 second, and all the programs are in RAM.

> Most users load initrd from a disk not by -initrd option.

It's unusual, but on my production webserver I use -kernel and -initrd
options explicitly.  That's because I want all my VMs to share a
single kernel.

virt-install is another program that uses explicit -initrd.

Rich.

-- 
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