linux-kernel - Re: [RFC] ELF Relocatable x86 and x86

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Message-ID: <20060804233815.GG18792@redhat.com>
Date:	Fri, 4 Aug 2006 19:38:15 -0400
From:	Dave Jones <davej@...hat.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	vgoyal@...ibm.com, fastboot@...l.org, linux-kernel@...r.kernel.org,
	Horms <horms@...ge.net.au>,
	Jan Kratochvil <lace@...kratochvil.net>,
	"H. Peter Anvin" <hpa@...or.com>,
	Magnus Damm <magnus.damm@...il.com>,
	Linda Wang <lwang@...hat.com>
Subject: Re: [RFC] ELF Relocatable x86 and x86_64 bzImages

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 ;-)

		Dave

-- 
http://www.codemonkey.org.uk
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