From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Lameter Date: Fri, 13 Oct 2006 01:12:21 +0000 Subject: RE: [RFC] Variable Kernel Page size support Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org On Thu, 12 Oct 2006, Chen, Kenneth W wrote: > > If set then a lookup is performed using the region7_pgdir table. > > That table is segmented into 8 section for the varying page > > sizes supported. > > What is the reason to anchor these 8 sections with pgdir? Can't we just > extract page size directly from the virtual address? Chop off bit 54 - 60, > that's the physical address, whola. I don't see why it can't be done. Yes we are chopping off the page size from the virtual address. But we need a page table to get to the physical address. That is what region7_pgdir is for. And it has different sections because that enables concurrent use of various page sizes in region 7. If pages with multiple page sizes would be in the same page table then we would have strange page number overlap scenarios to deal with.