From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756372AbZCFRTV (ORCPT ); Fri, 6 Mar 2009 12:19:21 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754717AbZCFRTM (ORCPT ); Fri, 6 Mar 2009 12:19:12 -0500 Received: from cam-admin0.cambridge.arm.com ([193.131.176.58]:47483 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754352AbZCFRTL (ORCPT ); Fri, 6 Mar 2009 12:19:11 -0500 Subject: Re: Regression - locking (all from 2.6.28) From: Catalin Marinas To: Dave Hansen Cc: Andrew Morton , jan sonnek , linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk, Peter Zijlstra , Andy Whitcroft In-Reply-To: <1236358369.10626.58.camel@nimitz> References: <49AC334A.9030800@gmail.com> <20090302121127.e46dc4be.akpm@linux-foundation.org> <1236076864.8547.20.camel@pc1117.cambridge.arm.com> <1236092480.8547.67.camel@pc1117.cambridge.arm.com> <1236214452.22399.68.camel@nimitz> <1236357616.3882.66.camel@pc1117.cambridge.arm.com> <1236358369.10626.58.camel@nimitz> Content-Type: text/plain Organization: ARM Ltd Date: Fri, 06 Mar 2009 17:18:08 +0000 Message-Id: <1236359888.3882.77.camel@pc1117.cambridge.arm.com> Mime-Version: 1.0 X-Mailer: Evolution 2.22.3.1 Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 06 Mar 2009 17:18:22.0639 (UTC) FILETIME=[8D5B83F0:01C99E7F] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2009-03-06 at 08:52 -0800, Dave Hansen wrote: > On Fri, 2009-03-06 at 16:40 +0000, Catalin Marinas wrote: > > It seems that node_start_pfn() isn't present on all the architectures. I > > ended up with something like below: > > > > + /* struct page scanning for each node */ > > + for_each_online_node(i) { > > + pg_data_t *pgdat = NODE_DATA(i); > > + unsigned long start_pfn = pgdat->node_start_pfn; > > + unsigned long end_pfn = start_pfn + > > + pgdat->node_spanned_pages - 1; > > + unsigned long pfn; > > + > > + for (pfn = start_pfn; pfn < end_pfn; pfn++) { > > + struct page *page; > > + > > + if (!pfn_valid(pfn)) > > + continue; > > + page = pfn_to_page(pfn); > > + /* only scan if page is in use */ > > + if (page_count(page) == 0) > > + continue; > > + scan_block(page, page + 1, NULL); > > + } > > + } > > What does scan_block() actually scan? Is that second argument > inclusive? No, it's exclusive. In the above case, it just scans a struct page at the given pointer. > I think you will miss scanning the contents of the last 'struct page' if > you do it this way because of the -1 you do to end_pfn. Fixed. > > Are the pgdat->node_start_pfn and pgdat->node_spanned_pages always > > valid? Thanks. > > The variables themselves? I'm sure there's a window in early boot where > they aren't valid, but other than that they should be OK unless you're > int the middle of a hotplug operation. > > See pgdat_resize_(un)lock() in include/linux/memory_hotplug.h. I wouldn't hold a lock for that long. It's not really critical to scan all the page structures at a time as there are subsequent scans as well, so some can be missed. -- Catalin