Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750771AbVI1Ub1 (ORCPT ); Wed, 28 Sep 2005 16:31:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750827AbVI1Ub0 (ORCPT ); Wed, 28 Sep 2005 16:31:26 -0400 Received: from e3.ny.us.ibm.com ([32.97.182.143]:44519 "EHLO e3.ny.us.ibm.com") by vger.kernel.org with ESMTP id S1750771AbVI1Ub0 (ORCPT ); Wed, 28 Sep 2005 16:31:26 -0400 Subject: Re: [PATCH 1/3 htlb-get_user_pages] Demand faulting for huge pages From: Adam Litke To: akpm@osdl.org Cc: "ADAM G. LITKE [imap]" , linux-kernel@vger.kernel.org, linux-mm@kvack.org In-Reply-To: <1127939141.26401.32.camel@localhost.localdomain> References: <1127939141.26401.32.camel@localhost.localdomain> Content-Type: text/plain Organization: IBM Date: Wed, 28 Sep 2005 15:31:18 -0500 Message-Id: <1127939478.26401.34.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.2.1.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1846 Lines: 51 Initial Post (Thu, 18 Aug 2005) In preparation for hugetlb demand faulting, remove this get_user_pages() optimization. Since huge pages will no longer be prefaulted, we can't assume that the huge ptes are established and hence, calling follow_hugetlb_page() is not valid. With the follow_hugetlb_page() call removed, the normal code path will be triggered. follow_page() will either use follow_huge_addr() or follow_huge_pmd() to check for a previously faulted "page" to return. When this fails (ie. with demand faults), __handle_mm_fault() gets called which invokes the hugetlb_fault() handler to instantiate the huge page. This patch doesn't make a lot of sense by itself, but I've broken it out to facilitate discussion on this specific element of the demand fault changes. While coding this up, I referenced previous discussion on this topic starting at http://lkml.org/lkml/2004/4/13/176 , which contains more opinions about the correctness of this approach. Diffed against 2.6.14-rc2-git6 Signed-off-by: Adam Litke --- memory.c | 5 ----- 1 files changed, 5 deletions(-) diff -upN reference/mm/memory.c current/mm/memory.c --- reference/mm/memory.c +++ current/mm/memory.c @@ -949,11 +949,6 @@ int get_user_pages(struct task_struct *t || !(flags & vma->vm_flags)) return i ? : -EFAULT; - if (is_vm_hugetlb_page(vma)) { - i = follow_hugetlb_page(mm, vma, pages, vmas, - &start, &len, i); - continue; - } spin_lock(&mm->page_table_lock); do { int write_access = write; -- Adam Litke - (agl at us.ibm.com) IBM Linux Technology Center - 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/