From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx167.postini.com [74.125.245.167]) by kanga.kvack.org (Postfix) with SMTP id 44D426B0062 for ; Wed, 28 Nov 2012 19:09:24 -0500 (EST) Received: from /spool/local by e3.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 28 Nov 2012 19:09:23 -0500 Received: from d01relay05.pok.ibm.com (d01relay05.pok.ibm.com [9.56.227.237]) by d01dlp03.pok.ibm.com (Postfix) with ESMTP id 95B3FC90044 for ; Wed, 28 Nov 2012 19:04:04 -0500 (EST) Received: from d01av04.pok.ibm.com (d01av04.pok.ibm.com [9.56.224.64]) by d01relay05.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id qAT044vd340438 for ; Wed, 28 Nov 2012 19:04:04 -0500 Received: from d01av04.pok.ibm.com (loopback [127.0.0.1]) by d01av04.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id qAT043jS005324 for ; Wed, 28 Nov 2012 19:04:04 -0500 Message-ID: <50B6A66E.8030406@linux.vnet.ibm.com> Date: Wed, 28 Nov 2012 16:03:58 -0800 From: Dave Hansen MIME-Version: 1.0 Subject: 32/64-bit NUMA consolidation behavior regresion Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Tejun Heo , LKML , linux-mm@kvack.org, Cody P Schafer Hi Tejun, I was bisecting a boot problem on a 32-bit NUMA kernel and it bisected down to commit 8db78cc4. It turns out that, with this patch, pcpu_need_numa() changed its return value on my system from 1 to 0. What that basically meant was that we stopped using the remapped lowmem areas for percpu data. My system is just qemu booted with: -smp 8 -m 8192 -numa node,nodeid=0,cpus=0-3 -numa node,nodeid=1,cpus=4-7 Watch the "PERCPU:" line early in boot, and you can see the "Embedded" come and go with or without your patch: [ 0.000000] PERCPU: Embedded 11 pages/cpu @f3000000 s30592 r0 d14464 vs [ 0.000000] PERCPU: 11 4K pages/cpu @f83fe000 s30592 r0 d14464 I believe this has to do with the hunks in your patch that do: -#ifdef CONFIG_X86_64 init_cpu_to_node(); -#endif ... -#ifdef CONFIG_X86_32 -DEFINE_EARLY_PER_CPU(int, x86_cpu_to_node_map, 0); -#else DEFINE_EARLY_PER_CPU(int, x86_cpu_to_node_map, NUMA_NO_NODE); -#endif EXPORT_EARLY_PER_CPU_SYMBOL(x86_cpu_to_node_map); I don't have a fix handy because I'm working on the original problem, but I just happened to run across this during a bisect. -- 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