From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757931AbdJMLmy (ORCPT ); Fri, 13 Oct 2017 07:42:54 -0400 Received: from ozlabs.org ([103.22.144.67]:35541 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751889AbdJMLmx (ORCPT ); Fri, 13 Oct 2017 07:42:53 -0400 From: Michael Ellerman To: Vlastimil Babka , Michal Hocko Cc: Andrew Morton , KAMEZAWA Hiroyuki , Reza Arbab , Yasuaki Ishimatsu , qiuxishi@huawei.com, Igor Mammedov , Vitaly Kuznetsov , linux-mm@kvack.org, LKML Subject: Re: [PATCH 1/2] mm, memory_hotplug: do not fail offlining too early In-Reply-To: References: <20170918070834.13083-1-mhocko@kernel.org> <20170918070834.13083-2-mhocko@kernel.org> <87bmlfw6mj.fsf@concordia.ellerman.id.au> <20171010122726.6jrfdzkscwge6gez@dhcp22.suse.cz> <87infmz9xd.fsf@concordia.ellerman.id.au> <20171011065123.e7jvoftmtso3vcha@dhcp22.suse.cz> Date: Fri, 13 Oct 2017 22:42:46 +1100 Message-ID: <87bmlbtgsp.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Vlastimil Babka writes: > On 10/11/2017 08:51 AM, Michal Hocko wrote: >> On Wed 11-10-17 13:37:50, Michael Ellerman wrote: >>> Michal Hocko writes: >>>> On Tue 10-10-17 23:05:08, Michael Ellerman wrote: >>>>> Michal Hocko writes: >>>>>> From: Michal Hocko >>>>>> >>>>>> Memory offlining can fail just too eagerly under a heavy memory pressure. ... >>>>> >>>>> This breaks offline for me. >>>>> >>>>> Prior to this commit: >>>>> /sys/devices/system/memory/memory0# time echo 0 > online >>>>> -bash: echo: write error: Device or resource busy > > Well, that means offline didn't actually work for that block even before > this patch, right? Is it even a movable_node block? I guess not? Correct. It should fail. >>>>> After: >>>>> /sys/devices/system/memory/memory0# time echo 0 > online >>>>> -bash: echo: write error: Device or resource busy >>>>> >>>>> real 2m0.009s >>>>> user 0m0.000s >>>>> sys 1m25.035s >>>>> >>>>> There's no way that block can be removed, it contains the kernel text, >>>>> so it should instantly fail - which it used to. > > Ah, right. So your complain is really about that the failure is not > instant anymore for blocks that can't be offlined. Yes. Previously it failed instantly, now it doesn't fail, and loops infinitely (once the 2 minute limit is removed). >> This is really strange! As you write in other email the page is >> reserved. That means that some of the earlier checks >> if (zone_idx(zone) == ZONE_MOVABLE) >> return false; >> mt = get_pageblock_migratetype(page); >> if (mt == MIGRATE_MOVABLE || is_migrate_cma(mt)) > > The MIGRATE_MOVABLE check is indeed bogus, because that doesn't > guarantee there are no unmovable pages in the block (CMA block OTOH > should be a guarantee). OK I'll try that and get back to you. cheers >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index 3badcedf96a7..5b4d85ae445c 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -7355,9 +7355,6 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, >> */ >> if (zone_idx(zone) == ZONE_MOVABLE) >> return false; >> - mt = get_pageblock_migratetype(page); >> - if (mt == MIGRATE_MOVABLE || is_migrate_cma(mt)) >> - return false; >> >> pfn = page_to_pfn(page); >> for (found = 0, iter = 0; iter < pageblock_nr_pages; iter++) { >> @@ -7368,6 +7365,9 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, >> >> page = pfn_to_page(check); >> >> + if (PageReserved(page)) >> + return true; >> + >> /* >> * Hugepages are not in LRU lists, but they're movable. >> * We need not scan over tail pages bacause we don't >>