From: Christoph Lameter <clameter@sgi.com>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: linux-ia64@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [RFC] virtual memmap for sparsemem [2/2] for ia64.
Date: Thu, 19 Oct 2006 18:45:18 -0700 (PDT) [thread overview]
Message-ID: <Pine.LNX.4.64.0610191842300.11820@schroedinger.engr.sgi.com> (raw)
In-Reply-To: <20061020103534.35a92813.kamezawa.hiroyu@jp.fujitsu.com>
On Fri, 20 Oct 2006, KAMEZAWA Hiroyuki wrote:
> Maximun phyisical address size of Itanium2 looks 50bits. Then, we need
> sizeof (struct page) * (50 - PAGE_SHIFT) size of virtual address space.
Right. That is 4TB which can be a portion of the 128TB VMALLOC space. Have
you seen my patchset that does the calculation on linux-ia674?
>
> #ifdef CONFIG_PGTABLE_4
> #define PGDIR_SHIFT (PUD_SHIFT + (PTRS_PER_PTD_SHIFT))
> #else
> #define PGDIR_SHIFT (PMD_SHIFT + (PTRS_PER_PTD_SHIFT))
> #endif
>
> Then, considering PAGE_SHIFT=14 case,
> 4-level-page-table mapsize:(1 << (4 * PAGE_SHIFT - 9) -> (1 << 47)
> 3-level-page-table mapsize:(1 << (3 * PAGE_SHIFT - 6) -> (1 << 36)
You are missing one PAGE_SHIFT (the page that is referred to !)
3 level is 47. 4 level is 58.
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next prev parent reply other threads:[~2006-10-20 1:45 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-10-19 8:23 KAMEZAWA Hiroyuki
2006-10-19 15:23 ` Andy Whitcroft
2006-10-20 1:20 ` KAMEZAWA Hiroyuki
2006-10-19 16:41 ` Christoph Lameter
2006-10-20 1:35 ` KAMEZAWA Hiroyuki
2006-10-20 1:45 ` Christoph Lameter [this message]
2006-10-20 2:08 ` KAMEZAWA Hiroyuki
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