From: "H. Peter Anvin" <hpa@zytor.com>
To: Chetan Nanda <chetannanda@gmail.com>
Cc: Venkatram Tummala <venkatram867@gmail.com>,
Joel Fernandes <agnel.joel@gmail.com>,
Frank Hu <frank.hu.2001@gmail.com>,
hayfeng Lee <teklife.kernel@gmail.com>,
linux-kernel@vger.kernel.org, linux-kernel@zh-kernel.org,
kernelnewbies@nl.linux.org
Subject: Re: why choose 896MB to the start point of ZONE_HIGHMEM
Date: Tue, 06 Apr 2010 22:28:39 -0700 [thread overview]
Message-ID: <4BBC1807.1090004@zytor.com> (raw)
In-Reply-To: <u2o7f245da81004062105w1f7d3416n7855472d28e8bcfd@mail.gmail.com>
On 04/06/2010 09:05 PM, Chetan Nanda wrote:
>
> I have a question here, what if I have a 32bit system with 2GB of RAM,
> so in that case my 896MB - 2GB RAM would be in accessible?
> What my understanding on the subject is:
> Only 896 MB of physical RAM is directly mapped on to kernel 1G virtual
> address space. And we still require page table settings to do that (page
> table would be identity mapping). But for rest of RAM, i.e. whenever
> there is need to access physical RAM beyond 896MB then that page will be
> mapped on to pages from 128MB kernel virtual address space (1GB - 896MB
> = 128MB), and AFAIK kmap is just for that.
>
> Please correct me if i am wrong
>
Correct.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
next prev parent reply other threads:[~2010-04-07 5:38 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-06 14:37 why choose 896MB to the start point of ZONE_HIGHMEM hayfeng Lee
2010-04-06 15:02 ` Joel Fernandes
2010-04-06 18:17 ` H. Peter Anvin
2010-04-06 19:20 ` Frank Hu
2010-04-06 19:44 ` H. Peter Anvin
2010-04-06 20:01 ` Joel Fernandes
2010-04-06 20:04 ` H. Peter Anvin
[not found] ` <q2iacff6c2b1004061528t28f1337eq977aabf8fe71bc22@mail.gmail.com>
[not found] ` <3715922601579231267@unknownmsgid>
2010-04-06 23:32 ` H. Peter Anvin
2010-04-07 1:47 ` Xianghua Xiao
[not found] ` <n2uacff6c2b1004061904v5d290fa6v909e2e5fe32ff910@mail.gmail.com>
2010-04-07 2:09 ` H. Peter Anvin
[not found] ` <n2jacff6c2b1004062248w311d8482w6c64a7bdfded8385@mail.gmail.com>
2010-04-07 12:10 ` Xianghua Xiao
[not found] ` <k2z7f245da81004070550u5324f6ffyba3e996a3e292a0a@mail.gmail.com>
[not found] ` <n2kb114f3281004070948hb510b9b1o80126e2411a98c8d@mail.gmail.com>
2010-04-07 17:14 ` H. Peter Anvin
2010-04-08 2:23 ` Nobin Mathew
[not found] ` <u2o7f245da81004062105w1f7d3416n7855472d28e8bcfd@mail.gmail.com>
2010-04-07 5:28 ` H. Peter Anvin [this message]
[not found] ` <h2pacff6c2b1004062257mc8552d81u33322c43e47502c9@mail.gmail.com>
2010-04-07 6:04 ` H. Peter Anvin
[not found] ` <q2oc58e39921004062208z6410b031o8d5654a582cc2783@mail.gmail.com>
[not found] ` <t2yacff6c2b1004062309t89b6bddfy3b0cf5970846fbb0@mail.gmail.com>
2010-04-07 14:11 ` tek-life
2010-04-06 20:15 ` Frank Hu
2010-04-06 20:18 ` H. Peter Anvin
2010-04-07 12:16 ` Krzysztof Halasa
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