Re: [RFC] ELF Relocatable x86 and x86_64 bzImages

From: H. Peter Anvin
Date: Fri Aug 04 2006 - 19:46:15 EST

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.


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