From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f199.google.com (mail-wr0-f199.google.com [209.85.128.199]) by kanga.kvack.org (Postfix) with ESMTP id 35A416B0253 for ; Wed, 11 Oct 2017 02:51:30 -0400 (EDT) Received: by mail-wr0-f199.google.com with SMTP id 22so349407wrb.9 for ; Tue, 10 Oct 2017 23:51:30 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id v21si11701643wra.442.2017.10.10.23.51.28 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 10 Oct 2017 23:51:28 -0700 (PDT) Date: Wed, 11 Oct 2017 08:51:23 +0200 From: Michal Hocko Subject: Re: [PATCH 1/2] mm, memory_hotplug: do not fail offlining too early Message-ID: <20171011065123.e7jvoftmtso3vcha@dhcp22.suse.cz> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87infmz9xd.fsf@concordia.ellerman.id.au> Sender: owner-linux-mm@kvack.org List-ID: To: Michael Ellerman Cc: Andrew Morton , KAMEZAWA Hiroyuki , Reza Arbab , Yasuaki Ishimatsu , qiuxishi@huawei.com, Igor Mammedov , Vitaly Kuznetsov , linux-mm@kvack.org, LKML , Vlastimil Babka 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. > >> > > >> > [ 5410.336792] page:ffffea22a646bd00 count:255 mapcount:252 mapping:ffff88ff926c9f38 index:0x3 > >> > [ 5410.336809] flags: 0x9855fe40010048(uptodate|active|mappedtodisk) > >> > [ 5410.336811] page dumped because: isolation failed > >> > [ 5410.336813] page->mem_cgroup:ffff8801cd662000 > >> > [ 5420.655030] memory offlining [mem 0x18b580000000-0x18b5ffffffff] failed > >> > > >> > Isolation has failed here because the page is not on LRU. Most probably > >> > because it was on the pcp LRU cache or it has been removed from the LRU > >> > already but it hasn't been freed yet. In both cases the page doesn't look > >> > non-migrable so retrying more makes sense. > >> > >> 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 > >> > >> real 0m0.001s > >> user 0m0.000s > >> sys 0m0.001s > >> > >> 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. > > > > OK, that means that start_isolate_page_range should have failed but it > > hasn't for some reason. I strongly suspect has_unmovable_pages is doing > > something wrong. Is the kernel text marked somehow? E.g. PageReserved? > > I'm not sure how the text is marked, will have to dig into that. > > > In other words, does the diff below helps? > > No that doesn't help. 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)) return false; has bailed out early. I would be quite surprised if the kernel text was sitting in the zone movable. The migrate type check is more fishy AFAICS. I can imagine that the kernel text can share the movable or CMA mt block. I am not really familiar with this function but it looks suspicious. So does it help to remove this check? --- 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 -- Michal Hocko SUSE Labs -- 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