Re: x86-64: Kernel with large page size

[William Lee Irwin III <wli@holomorphy.com>]

On Fri, Jun 03, 2005 at 05:50:55PM -0700, Subrahmanyam Ongole wrote:
> When we run our application on AMD Opteron processors, we are seeing a
> large number of   L1_AND_L2_DTLB_MISSES. We used oprofile to measure
> these numbers.
> We wanted to try with a bigger page size and see if we could bring it
> down. TLB caches 4k page translations. I don't  know if larger page
> size would even help here.
> I  changed PAGE_SHIFT to 14 ( 16k page size ) in include/asm/page.h
> and recompiled kernel and modules.   It crashed ( PANIC: early
> exception ) at the very initial stage of loading the image.
> I looked at some of the mailing list archives for any information on
> this. I couldn't find anything on this subject . I appreciate any help
> on this.
> There seem to be two 2-4MB page translations in L1 TLB cache on AMD
> machines. Will it be used only when the page size is 2MB or can they
> be used with smaller page sizes too.

PAGE_SIZE at the moment is intimately tied to the MMU's notions of
address translation, which are determined by hardware.


-- wli