Subject: Re: 4MB pages?
To: None <>
From: Matt Thomas <>
List: tech-kern
Date: 09/06/2000 08:16:42
At 07:11 AM 9/6/2000 -0700, Jason R Thorpe wrote:
>On Wed, Sep 06, 2000 at 02:10:05PM +0200, Hubert Feyrer wrote:
>  > Seeing this jump from few kb pages to few MB pages looks ... interresting.
>  > What's the background on this?
>  > Is it intended to make switch pagesize on i386 unconditionally?
>No, the i386 port will use a combination of 4K and 4MB pages.  The idea is
>to use a 4MB page for the kernel text+data+bss to reduce TLB usage for the
>kernel, thus improving overall performance.
>See the Intel IA32 system programmers reference manual.

For memory intensive (mmap large files, etc.) programs, I was wondering whether
it would be useful to have another uvm free page area which contains free 4MB
blocks.  As memory gets freed, as a complete 4MB block is freed it would be
moved to the free 4MB list.

4MB page table entries would be real useful for mapping framebuffers as 
well but
that requires a[nother] change to the driver mmap interface.

Note that these idea are applicable to other architectures that support 
such as alpha.
Matt Thomas               Internet:
3am Software Foundry      WWW URL:
Cupertino, CA             Disclaimer: I avow all knowledge of this message