linux-kernel - Re: [PATCH] x86-64: improve e820_search

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Message-ID: <20090508205347.GC23223@one.firstfloor.org>
Date:	Fri, 8 May 2009 22:53:47 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Jan Beulich <jbeulich@...ell.com>, mingo@...e.hu,
	tglx@...utronix.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86-64: improve e820_search_gap()

On Fri, May 08, 2009 at 01:15:38PM -0700, H. Peter Anvin wrote:
> Andi Kleen wrote:
> >"Jan Beulich" <jbeulich@...ell.com> writes:
> >>Why blindly? Aren't hotpluggable memory ranges supposed to be reserved
> >>in the E820 map?
> >
> >They are supposed to be reserved in SRAT, but not in e820.
> 
> Ah, okay.  Perhaps we should fold this information into our internal 
> "e820" map?  If so I guess the question is how soon we can do that.

You could do that or just query SRAT too, but ...

The problem is really that there are still systems which have hidden
holes which are not reserved anywhere. When I last hacked on the gap algorithm
it triggered subtle bugs. So this will never be fully reliable.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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