Re: [Qemu-devel] guest kernel in the host RAM

[Denis V. Lunev]

On 12/15/2015 02:59 PM, Paolo Bonzini wrote:
> On 15/12/2015 12:27, Denis V. Lunev wrote:
> > The idea is that we could boot with the uncompressed Linux
> > kernel in the guest which serves 2 purposes:
> > - faster boot time as per Intel opinion
> > - memory savings
> >
> > Uncompressed kernel image could be the same for several
> > guests and thus memory pages for the kernel could be the
> > same, which saves a bit of RAM :)
> >
> > At the moment neither BIOS support this in full: nor SeaBIOS,
> > nor OVMF, nor QBoot.
> >
> >  From our point of view QBoot is an ideal candidate for this.
> QBoot is not meant for use in production; SeaBIOS actually is just as
> fast if you configure it right.
>
> > Do you have any opinion for the topic?
> I honestly don't like the idea.  Linux patches itself a lot, which
> makes the memory savings minimal (if they exist at all).  What is the
> decompression time for a kernel that is compressed with LZO?
>
> Paolo
It seems that you are perfectly correct here!

With large pages enabled (and preferred 2 Mb pages mode)
we will have exactly zero bonus.

Thank you for saving a lot of time and efforts :)))

Den