Re: [Qemu-devel] Slow kernel/initrd loading via fw_cfg; Was Re: Hack integrating SeaBios / LinuxBoot option rom with QEMU trace backends

[Richard W.M. Jones]

On Tue, Oct 11, 2011 at 09:23:15AM +0100, Daniel P. Berrange wrote:
>  - libguestfs directly boots its appliance using the regular host's
>    kernel image and a custom built initrd image. The initrd does
>    not contain the entire appliance, just enough to boot up and
>    dynamically read files in from the host OS on demand. This is
>    a so called "supermin appliance".
> 
>    The kernel is < 5 MB, while the initrd is approx 100MB.
[...]

Actually this is how libguestfs used to work, but the performance of
such a large initrd against the poor qemu implementation meant we had
to abandon this approach.

We now use -kernel ~5MB, a small -initrd ~1.1MB and a large ext2
format root disk (of course loaded on demand, which is better anyway).

Nevertheless any improvement in -kernel and -initrd load times would
help us a gain a few 1/10ths of seconds, which is still very important
for us.  Overall boot time is 3-4 seconds and we are often in a
situation where we need to repeatedly boot the appliance.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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