From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e28smtp07.in.ibm.com (e28smtp07.in.ibm.com [122.248.162.7]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 7ECA42C009B for ; Wed, 26 Feb 2014 18:52:26 +1100 (EST) Received: from /spool/local by e28smtp07.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 26 Feb 2014 13:22:21 +0530 Received: from d28relay03.in.ibm.com (d28relay03.in.ibm.com [9.184.220.60]) by d28dlp03.in.ibm.com (Postfix) with ESMTP id E24781258053 for ; Wed, 26 Feb 2014 13:24:23 +0530 (IST) Received: from d28av05.in.ibm.com (d28av05.in.ibm.com [9.184.220.67]) by d28relay03.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id s1Q7q3ZI9240920 for ; Wed, 26 Feb 2014 13:22:04 +0530 Received: from d28av05.in.ibm.com (localhost [127.0.0.1]) by d28av05.in.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s1Q7qHJH023983 for ; Wed, 26 Feb 2014 13:22:18 +0530 From: "Aneesh Kumar K.V" To: Andrew Morton , Liu Ping Fan Subject: Re: [PATCH] mm: numa: bugfix for LAST_CPUPID_NOT_IN_PAGE_FLAGS In-Reply-To: <20140213152009.b16a30d2a5b5c5706fc8952a@linux-foundation.org> References: <1391563546-26052-1-git-send-email-pingfank@linux.vnet.ibm.com> <20140213152009.b16a30d2a5b5c5706fc8952a@linux-foundation.org> Date: Wed, 26 Feb 2014 13:22:16 +0530 Message-ID: <87k3cifgzz.fsf@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain Cc: Peter Zijlstra , linux-mm@kvack.org, Paul Mackerras , linuxppc-dev@lists.ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Andrew Morton writes: > On Wed, 5 Feb 2014 09:25:46 +0800 Liu Ping Fan wrote: > >> When doing some numa tests on powerpc, I triggered an oops bug. I find >> it is caused by using page->_last_cpupid. It should be initialized as >> "-1 & LAST_CPUPID_MASK", but not "-1". Otherwise, in task_numa_fault(), >> we will miss the checking (last_cpupid == (-1 & LAST_CPUPID_MASK)). >> And finally cause an oops bug in task_numa_group(), since the online cpu is >> less than possible cpu. > > I grabbed this. I added this to the changelog: > > : PPC needs the LAST_CPUPID_NOT_IN_PAGE_FLAGS case because ppc needs to > : support a large physical address region, up to 2^46 but small section size > : (2^24). So when NR_CPUS grows up, it is easily to cause > : not-in-page-flags. > > to hopefully address Peter's observation. > > How should we proceed with this? I'm getting the impression that numa > balancing on ppc is a dead duck in 3.14, so perhaps this and > > powerpc-mm-add-new-set-flag-argument-to-pte-pmd-update-function.patch > mm-dirty-accountable-change-only-apply-to-non-prot-numa-case.patch > mm-use-ptep-pmdp_set_numa-for-updating-_page_numa-bit.patch > All these are already in 3.14 ? > are 3.15-rc1 material? > We should push the first hunk to 3.14. I will wait for Liu to redo the patch. BTW this should happen only when SPARSE_VMEMMAP is not specified. Srikar had reported the issue here http://mid.gmane.org/20140219180200.GA29257@linux.vnet.ibm.com #if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP) #define SECTIONS_WIDTH SECTIONS_SHIFT #else #define SECTIONS_WIDTH 0 #endif -aneesh