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SubjectRe: Topic for discussion: OS Design
Date
On Thu, 26 Oct 2000 09:17:49 -0400 (EDT), 
"Richard B. Johnson" <root@chaos.analogic.com> wrote:
>On Thu, 26 Oct 2000, Albert D. Cahalan wrote:
>> I doubt this is true on most modern processors. On the Pentium
>> and above, large pages are used for the kernel. The PowerPC port
> ^^^^^^^^^^^
>
>The page-size is determined by the architecture. They are 4096 bytes
>in the pentium. /usr/include/asm/page.h PAGE_SHIFT = 12, PAGE_SIZE =
>1 << PAGE_SHIFT.

ADC probably meant "large page tables" as opposed to "large pages".
Instead of one page table entry per 4K page, Pentium supports PTEs for
contiguous collections of pages, less activity on the page tables
generally results in better performance.

>This shows that out of 34,678 bytes we needed, we wasted 6282, ~1.5
>pages. Since there are 5 modules, we waste about 1/3 page per module.
>
>So I don't, as you say; "... waste 1/2 page or more per module".

Statistics say that the average loss will be 1/2 page per module. Some
will waste more, some will waste less, average is 1/2 the unit.

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