From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Bob Picco" Date: Fri, 5 May 2006 12:18:31 -0400 Subject: Re: assert/crash in __rmqueue() when enabling CONFIG_NUMA Message-ID: <20060505161831.GB5708@localhost> References: <20060504013239.GG19859@localhost> <1146756066.22503.17.camel@localhost.localdomain> <20060504154652.GA4530@localhost> <20060504192528.GA26759@elte.hu> <20060504194334.GH19859@localhost> <445A7725.8030401@shadowen.org> <20060505135503.GA5708@localhost> <1146839590.22503.48.camel@localhost.localdomain> <20060505145018.GI19859@localhost> <1146841064.22503.53.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1146841064.22503.53.camel@localhost.localdomain> Sender: owner-linux-mm@kvack.org Return-Path: To: Dave Hansen Cc: Bob Picco , Andy Whitcroft , Ingo Molnar , Nick Piggin , "Martin J. Bligh" , Andi Kleen , linux-kernel@vger.kernel.org, Andrew Morton , Linux Memory Management List-ID: Dave Hansen wrote: [Fri May 05 2006, 10:57:44AM EDT] > On Fri, 2006-05-05 at 10:50 -0400, Bob Picco wrote: > > Dave Hansen wrote: [Fri May 05 2006, 10:33:10AM EDT] > > > The page_zonenum() checks look good, but I'm not sure I understand the > > > page_in_zone_hole() part. If a page is in a hole in a zone, it will > > > still have a valid mem_map entry, right? It should also never have been > > > put into the allocator, so it also won't ever be coalesced. > > This has always been subtle and not too revealing. It probably should > > have a comment. The page_in_zone_hole check is for ia64 > > VIRTUAL_MEM_MAP. You might compute a page structure which is in a hole not > > backed by memory; an unallocated page which covers pages structures. > > VIRTUAL_MEM_MAP uses a contiguous virtual region with virtual space holes > > not backed by memory. Take a look at ia64_pfn_valid. > > Ahhh. I hadn't made the ia64 connection. I wonder if it is worth > making CONFIG_HOLES_IN_ZONE say ia64 or something about vmem_map in it > somewhere. Might be worth at least a comment like this: > > + if (page_in_zone_hole(buddy)) /* noop on all but ia64 */ > + break; > + else if (page_zonenum(buddy) != page_zonenum(page)) > + break; > + else if (!page_is_buddy(buddy, order)) > break; /* Move the buddy up one level. */ > > BTW, wasn't the whole idea of discontig to have holes in zones (before > NUMA) without tricks like this? ;) Sure you could boot ia64 with just DISCONTIGMEM and no VIRTUAL_MEM_MAP. In fact that's exactly what I did to test code added in alloc_node_mem_map. Unfortunately I was missing 1Gb from free memory after booting. The missing 1Gb was consumed by reserved pages structures :) > > -- Dave > bob -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org