Re: PAE and PSE ??
From: H. Peter Anvin
Date: Sun Oct 22 2006 - 19:38:08 EST
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
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