From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [66.187.233.31]) by ozlabs.org (Postfix) with ESMTP id 1581EDDE05 for ; Tue, 4 Dec 2007 08:55:56 +1100 (EST) Message-ID: <47547A79.2060206@redhat.com> Date: Mon, 03 Dec 2007 16:51:53 -0500 From: Chris Snook MIME-Version: 1.0 To: kniht@linux.vnet.ibm.com, linuxppc-dev , Linux Memory Management List Subject: Re: [PATCH 2/2] powerpc: make 64K huge pages more reliable References: <474CF694.8040700@us.ibm.com> <20071203020648.GF26919@localhost.localdomain> In-Reply-To: <20071203020648.GF26919@localhost.localdomain> Content-Type: text/plain; charset=ISO-8859-1; format=flowed List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , David Gibson wrote: > On Tue, Nov 27, 2007 at 11:03:16PM -0600, Jon Tollefson wrote: >> This patch adds reliability to the 64K huge page option by making use of >> the PMD for 64K huge pages when base pages are 4k. So instead of a 12 >> bit pte it would be 7 bit pmd and a 5 bit pte. The pgd and pud offsets >> would continue as 9 bits and 7 bits respectively. This will allow the >> pgtable to fit in one base page. This patch would have to be applied >> after part 1. > > Hrm.. shouldn't we just ban 64K hugepages on a 64K base page size > setup? There's not a whole lot of point to it, after all... > Actually, it sounds to me like an ideal way to benchmark the efficiency of the hugepage implementation and VM effects, without the TLB performance obscuring the results. I agree that it's not something people will want to do very often, but the same can be said about quite a lot of strange things that we allow just because there's no fundamental reason why they cannot be. -- Chris