From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Jan Beulich" <jbeulich@novell.com>
Subject: Re: Questions about memory zone
Date: Tue, 05 May 2009 09:25:32 +0100
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To: ruby young <yangyang@les.buaa.edu.cn>
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>>> ruby young <yangyang@les.buaa.edu.cn> 05.05.09 10:05 >>>
>Hi, all~
>I'm interested in memory of xen. And I wondered what does the real mean =
of
>xen 'zone'. It seems different from linux 'zone'.
>In the source code of xen-3.3.0/xen/common/page_alloc.c, there is =
defined:
>#define pfn_dom_zone_type(_pfn) (fls(_pfn)-1)
>
>and NR_ZONES is defined:
>#define NR_ZONES (PADDR_BITS - PAGE_SHIFT)
>
>It seems Zone in xen set up as physic address and are separate by the =
last
>pfn bit set.

Correct.

>But Why does Xen Zone organize like this? And What does the Zone mean?

In order to be able to allocate memory based on address width restrictions,=

without adding overhead on sorting memory as it gets (or after it got) =
freed.

Jan