Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933472AbXKOV52 (ORCPT ); Thu, 15 Nov 2007 16:57:28 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1765782AbXKOV5P (ORCPT ); Thu, 15 Nov 2007 16:57:15 -0500 Received: from gw.goop.org ([64.81.55.164]:50203 "EHLO mail.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1765618AbXKOV5O (ORCPT ); Thu, 15 Nov 2007 16:57:14 -0500 Message-ID: <473CC0AC.3020500@goop.org> Date: Thu, 15 Nov 2007 13:57:00 -0800 From: Jeremy Fitzhardinge User-Agent: Thunderbird 2.0.0.5 (X11/20070727) MIME-Version: 1.0 To: William Lee Irwin III , Andi Kleen , Ingo Molnar , Linus Torvalds , Thomas Gleixner , Nick Piggin , "H. Peter Anvin" CC: Linux Kernel Mailing List Subject: Why preallocate pmd in x86 32-bit PAE? X-Enigmail-Version: 0.95.5 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 929 Lines: 21 I'm looking at unifying asm-x86/pgalloc*.h, and so I'm trying to make things as similar as possible between 32 and 64-bit. Once difference is that 64-bit incrementally allocates all levels of the pagetable, whereas 32-bit PAE preallocates the 4 pmds when it allocates the pgd. What's the rationale for this? What pitfalls would there be in making them incrementally allocated? Preallocation makes sense from the perspective that they will all be allocated almost immediately in a typical process. But it is a somewhat arbitrary difference from 64-bit, and since 64-bit can't reasonably preallocate any pagetable levels, it seems sensible to change 32-bit to match. Thanks, J - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/