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

["Daniel P. Berrange" <berrange@redhat.com>]

On Tue, Oct 11, 2011 at 11:39:36AM +0200, Avi Kivity wrote:
> On 10/11/2011 11:27 AM, Daniel P. Berrange wrote:
> >>  >For comparison I also did a test building a bootable ISO using ISOLinux.
> >>  >This required 700 ms for the boot time, which is appoximately 1/2 the
> >>  >time reqiured for direct kernel/initrd boot. But you have to then add
> >>  >on time required to build the ISO on every boot, to add custom kernel
> >>  >command line args. So while ISO is faster than LinuxBoot currently
> >>  >there is still non-negligable overhead here that I want to avoid.
> >>
> >>  You can accept parameters from virtio-serial or some other channel.
> >>  Is there any reason you need them specifically as *kernel* command
> >>  line parameters?
> >
> >Well some of the parameters are actually kernel parameters :-) The rest
> >are things I pass to the 'init' process which runs in the initrd. When
> >this process first starts the only things it can easily access are those
> >builtin to the kernel image, so data available from /proc or /sys like
> >the /proc/cmdline file. It hasn't even loaded things like the virtio-serial
> >or virtio-9pfs kernel modules at this point.
> >
> 
> It could, if it wanted to.  It's completely custom, yes?

I'm thinking primarily about debug related parameters, which need to be
used as soon the process starts, not delayed until after we've loaded
kernel modules at which point the step we wanted to debug is already
past.


Daniel
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