From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761359AbZENR2T (ORCPT ); Thu, 14 May 2009 13:28:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753715AbZENR2A (ORCPT ); Thu, 14 May 2009 13:28:00 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:49233 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752278AbZENR2A (ORCPT ); Thu, 14 May 2009 13:28:00 -0400 Date: Thu, 14 May 2009 10:25:54 -0700 From: Andrew Morton To: Yinghai Lu Cc: mel@csn.ul.ie, mingo@elte.hu, tglx@linutronix.de, hpa@zytor.com, cl@linux-foundation.org, suresh.b.siddha@intel.com, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk, rusty@rustcorp.com.au, steiner@sgi.com, rientjes@google.com Subject: Re: [PATCH 5/5] mm: clear N_HIGH_MEMORY map before se set it again -v2 Message-Id: <20090514102554.b3a36f19.akpm@linux-foundation.org> In-Reply-To: <4A0C4F67.5080802@kernel.org> References: <4A05269D.8000701@kernel.org> <20090512111623.GG25923@csn.ul.ie> <4A0A64FB.4080504@kernel.org> <20090513145950.GB28097@csn.ul.ie> <4A0C4910.7090508@kernel.org> <4A0C4A2A.6080009@kernel.org> <20090514095414.ba8356e5.akpm@linux-foundation.org> <4A0C4F67.5080802@kernel.org> X-Mailer: Sylpheed version 2.2.4 (GTK+ 2.8.20; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 14 May 2009 10:05:43 -0700 Yinghai Lu wrote: > Andrew Morton wrote: > > On Thu, 14 May 2009 09:43:22 -0700 > > Yinghai Lu wrote: > > > >> incase some system strange SRAT table. some kind of small range. > >> or with mem= etc > >> > > > > That description is very hard to understand. Please provide more details. > > if the wrong SRAT table, have small range for some node. that node will not be onlined. > In the early checking, the bit in node_states[N_HIGH_MEMORY] for the node is set even > that node has less RAM like 1M, and it is not cleared before the bit is set again in > the following loop according online nodes. Where in the kernel does this setting of the bit in node_states[] occur? early_calculate_totalpages()? Where in the kernel is it later decided to _not_ use these pages in that node? Perhaps that's the place where the problem should be fixed. > > > >> Signed-off-by: Yinghai Lu > >> Tested-by: Jack Steiner > > > > What reason did Jack have to test this? Perhaps he hit some bug? > > If so, please fully describe that bug in the changelog. > > for some memmoryless node and strange memmap. That's not a very good problem description. Put yourself in the position of a distro engineer whose customer reports a 2.6.26 problem. He's going to look at your patch wondering whether it might fix his customer's problem. We should provide him with sufficient information to be able to determine this. > > > > > >> Index: linux-2.6/mm/page_alloc.c > >> =================================================================== > >> --- linux-2.6.orig/mm/page_alloc.c > >> +++ linux-2.6/mm/page_alloc.c > >> @@ -4041,6 +4047,11 @@ void __init free_area_init_nodes(unsigne > >> early_node_map[i].start_pfn, > >> early_node_map[i].end_pfn); > >> > >> + /* > >> + * find_zone_movable_pfns_for_nodes/early_calculate_totalpages init > >> + * that node_mask, clear it at first > >> + */ > >> + nodes_clear(node_states[N_HIGH_MEMORY]); > >> /* Initialise every node */ > >> mminit_verify_pageflags_layout(); > >> setup_nr_node_ids(); > > > > If CONFIG_HIGHMEM=n, this will clear the N_NORMAL_MEMORY entry in > > node_states[]. Why is this correct and desirable? > > then N_NORMAL_MEMORY == N_HIGH_MEMORY I know. But it's unobvious that this change is correct and desirable with both CONFIG_HIGHMEM=n and CONFIG_HIGHMEM=y.