From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755941Ab2ITVmf (ORCPT ); Thu, 20 Sep 2012 17:42:35 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:34911 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753578Ab2ITVme (ORCPT ); Thu, 20 Sep 2012 17:42:34 -0400 Date: Thu, 20 Sep 2012 14:42:32 -0700 From: Andrew Morton To: Minchan Kim Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Kamezawa Hiroyuki , Yasuaki Ishimatsu , KOSAKI Motohiro Subject: Re: [PATCH v3] memory-hotplug: fix zone stat mismatch Message-Id: <20120920144232.a3e8b60f.akpm@linux-foundation.org> In-Reply-To: <1348123405-30641-1-git-send-email-minchan@kernel.org> References: <1348123405-30641-1-git-send-email-minchan@kernel.org> X-Mailer: Sylpheed 3.0.2 (GTK+ 2.20.1; x86_64-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, 20 Sep 2012 15:43:25 +0900 Minchan Kim wrote: > During memory-hotplug, I found NR_ISOLATED_[ANON|FILE] > are increasing so that kernel are hang out. > > The cause is that when we do memory-hotadd after memory-remove, > __zone_pcp_update clear out zone's ZONE_STAT_ITEMS in setup_pageset > although vm_stat_diff of all CPU still have value. > > In addtion, when we offline all pages of the zone, we reset them > in zone_pcp_reset without drain so that we lost zone stat item. > Here's what I ended up with for a changelog: : During memory-hotplug, I found NR_ISOLATED_[ANON|FILE] are increasing, : causing the kernel to hang. When the system doesn't have enough free : pages, it enters reclaim but never reclaim any pages due to : too_many_isolated()==true and loops forever. : : The cause is that when we do memory-hotadd after memory-remove, : __zone_pcp_update() clears a zone's ZONE_STAT_ITEMS in setup_pageset() : although the vm_stat_diff of all CPUs still have values. : : In addtion, when we offline all pages of the zone, we reset them in : zone_pcp_reset without draining so we loss some zone stat item. As memory hotplug seems fairly immature and broken, I'm thinking there's no point in backporting this into -stable. And I don't *think* we really need it in 3.6 either? (It doesn't apply cleanly to current mainline anyway - I didn't check why).