From: "H. Peter Anvin" <hpa@zytor.com>
To: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Sandeep Kumar <sandeepksinha@gmail.com>, linux-kernel@vger.kernel.org
Subject: Re: PAE and PSE ??
Date: Sun, 22 Oct 2006 16:37:27 -0700 [thread overview]
Message-ID: <453C00B7.3040909@zytor.com> (raw)
In-Reply-To: <200610221215.26525.rjw@sisk.pl>
Rafael J. Wysocki wrote:
> Hi,
>
> On Sunday, 22 October 2006 08:29, Sandeep Kumar wrote:
>> Hi all,
>> I have read in UTLK by bovet that the linux kernel does not uses the
>> PSE bit on an x86
>> machine. Then how come we have the hugetlbfs, which provides support
>> for 4MB pages ?
>
> AFAIK, PSE is only used when PAE is not set and then it enables the 4 MB
> pages. If PAE is set, the 4 MB pages are impossible because there are only
> 512 entries per page table, but 2 MB pages can be used instead (and you don't
> need to set PSE to use them).
>
You're wrong.
PSE refers to 4 MB pages when PAE is not used, and 2 MB pages when PAE
is used.
In theory, you could have PAE without PSE, which would only support 4K
pages.
Linux uses PSE; it may or may not use PAE depending on the configuration.
-hpa
next prev parent reply other threads:[~2006-10-22 23:37 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-10-22 6:29 PAE and PSE ?? Sandeep Kumar
2006-10-22 10:15 ` Rafael J. Wysocki
2006-10-22 23:37 ` H. Peter Anvin [this message]
2006-10-23 10:13 ` Rafael J. Wysocki
2006-10-23 14:10 ` H. Peter Anvin
2006-10-23 14:14 ` Rafael J. Wysocki
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