Re: [RFC] 4-level page table directories.

Robin Holt
2005-11-08T12:43:25Z

On Mon, Nov 07, 2005 at 04:22:32PM -0800, Rohit Seth wrote:
> I think using a 64K page size (may be make that default for IA-64 or
> distribute as another kernel the way SuSE has done) is preferred over
> 4-level page tables....particularly for big memory machines.

For your particular application, that may be the case. For approx half
of our customers, they _REQUIRE_ their application be certified by the
software vendor. The vendors usually try to limit their exposure by
certifiying on the smallest set kernel/modules/libraries possible.
We don't control that.

> There is always at least couple of percentage points that an application
> can gain with even smaller memory foot print (like few gig!) by using
> 64K page size for normal pages.

There is also the possibility that the app may be using the pages sparsely
and therefore wasting a larger percentage of time zeroing memory which
is never needed (smaller percent of page fill).

Thanks,
Robin