Re: [RFC] ELF Relocatable x86 and x86_64 bzImages

H. Peter Anvin
2006-08-04T23:47:37Z

Dave Jones wrote:
> On Fri, Aug 04, 2006 at 05:14:37PM -0600, Eric W. Biederman wrote:
>
> > I guess the practical question is do people see a real performance benefit
> > when loading the kernel at 4MB?
>
> Linus claimed lmbench saw some huge wins. Others showed that for eg,
> a kernel compile took the same amount of time, so take from that what you will..
>
> > Possibly the right solution is to do like I did on x86_64 and simply remove
> > CONFIG_PHYSICAL_START, and always place the kernel at 4MB, or something like
> > that.
> >
> > The practical question is what to do to keep the complexity from spinning
> > out of control. Removing CONFIG_PHYSICAL_START would seriously help with
> > that.
>
> Given the two primary uses of that option right now are a) the aforementioned
> perf win and b) building kexec kernels, I doubt anyone would miss it once
> we go relocatable ;-)
>

We DO want the performance gain with a conventional bootloader. The
perf win is about the location of the uncompressed kernel, not the
compressed kernel.

-hpa