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From: Michael Ellerman <mpe@ellerman.id.au>
To: Michal Hocko <mhocko@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
	Reza Arbab <arbab@linux.vnet.ibm.com>,
	Yasuaki Ishimatsu <yasu.isimatu@gmail.com>,
	qiuxishi@huawei.com, Igor Mammedov <imammedo@redhat.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>,
	Vlastimil Babka <vbabka@suse.cz>
Subject: Re: [PATCH 1/2] mm, memory_hotplug: do not fail offlining too early
Date: Wed, 11 Oct 2017 16:19:05 +1100
Message-ID: <87a80yz2gm.fsf@concordia.ellerman.id.au> (raw)
In-Reply-To: <87infmz9xd.fsf@concordia.ellerman.id.au>

Michael Ellerman <mpe@ellerman.id.au> writes:
> Michal Hocko <mhocko@kernel.org> writes:
>> On Tue 10-10-17 23:05:08, Michael Ellerman wrote:
>>> Michal Hocko <mhocko@kernel.org> writes:
>>> > From: Michal Hocko <mhocko@suse.com>
>>> > 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.

Yeah it's reserved:

  $ grep __init_begin /proc/kallsyms
  c000000000d70000 T __init_begin
  $ ./page-types -r -a 0x0,0xd7
               flags	page-count       MB  symbolic-flags			long-symbolic-flags
  0x0000000100000000	       215       13  __________________________r_______________	reserved
               total	       215       13


I added some printks, we're getting EBUSY from do_migrate_range(pfn, end_pfn).

So we seem to just have an infinite loop:

  repeat:
  	/* start memory hot removal */
  	ret = -EINTR;
  	if (signal_pending(current))
  		goto failed_removal;
  
  	cond_resched();
  	lru_add_drain_all_cpuslocked();
  	drain_all_pages(zone);
  
  	pfn = scan_movable_pages(start_pfn, end_pfn);
  	if (pfn) { /* We have movable pages */
  		ret = do_migrate_range(pfn, end_pfn);
  		printk_ratelimited("memory-hotplug: migrate range returned %ld\n", ret);
  		goto repeat;
  	}


eg:

  memory-hotplug: migrate range returned -16
  memory-hotplug: migrate range returned -16
  memory-hotplug: migrate range returned -16
  memory-hotplug: migrate range returned -16
  memory-hotplug: migrate range returned -16
  memory-hotplug: migrate range returned -16
  memory-hotplug: migrate range returned -16
  memory-hotplug: migrate range returned -16
  memory-hotplug: migrate range returned -16
  memory-hotplug: migrate range returned -16
  __offline_pages: 354031 callbacks suppressed
  memory-hotplug: migrate range returned -16
  memory-hotplug: migrate range returned -16
  memory-hotplug: migrate range returned -16
  memory-hotplug: migrate range returned -16
  memory-hotplug: migrate range returned -16
  memory-hotplug: migrate range returned -16
  memory-hotplug: migrate range returned -16
  memory-hotplug: migrate range returned -16
  memory-hotplug: migrate range returned -16
  memory-hotplug: migrate range returned -16
  __offline_pages: 355794 callbacks suppressed


cheers

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  reply index

Thread overview: 56+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-09-18  7:08 [PATCH v2 0/2] mm, memory_hotplug: redefine memory offline retry logic Michal Hocko
2017-09-18  7:08 ` [PATCH 1/2] mm, memory_hotplug: do not fail offlining too early Michal Hocko
2017-10-10 12:05   ` Michael Ellerman
2017-10-10 12:27     ` Michal Hocko
2017-10-11  2:37       ` Michael Ellerman
2017-10-11  5:19         ` Michael Ellerman [this message]
2017-10-11 14:05           ` Anshuman Khandual
2017-10-11 14:16             ` Michal Hocko
2017-10-11  6:51         ` Michal Hocko
2017-10-11  8:04           ` Vlastimil Babka
2017-10-11  8:13             ` Michal Hocko
2017-10-11 11:17               ` Vlastimil Babka
2017-10-11 11:24                 ` Michal Hocko
2017-10-13 11:42             ` Michael Ellerman
2017-10-13 11:58               ` Michal Hocko
2017-10-13 12:00                 ` [PATCH 1/2] mm: drop migrate type checks from has_unmovable_pages Michal Hocko
2017-10-13 12:00                   ` [PATCH 2/2] mm, page_alloc: fail has_unmovable_pages when seeing reserved pages Michal Hocko
2017-10-13 12:04                     ` Vlastimil Babka
2017-10-13 12:07                       ` Michal Hocko
2017-10-17 13:03                         ` Vlastimil Babka
2017-10-17 11:41                   ` [PATCH 1/2] mm: drop migrate type checks from has_unmovable_pages Michael Ellerman
2017-10-17 12:03                     ` Michal Hocko
2017-10-17 13:02                   ` Vlastimil Babka
2017-10-19  2:51                   ` Joonsoo Kim
2017-10-19  7:15                     ` Michal Hocko
2017-10-19  7:33                       ` Joonsoo Kim
2017-10-19  8:20                         ` Michal Hocko
2017-10-19 12:21                           ` Michal Hocko
2017-10-20  2:13                             ` Joonsoo Kim
2017-10-20  5:59                               ` Michal Hocko
2017-10-20  6:50                                 ` Joonsoo Kim
2017-10-20  7:02                                   ` Michal Hocko
2017-10-23  5:23                                     ` Joonsoo Kim
2017-10-23  8:10                                       ` Michal Hocko
2017-10-24  4:44                                         ` Joonsoo Kim
2017-10-24  7:44                                           ` Michal Hocko
2017-10-24  8:12                                           ` Vlastimil Babka
2017-10-24 12:25                                             ` Michal Hocko
2017-10-26  2:47                                             ` Joonsoo Kim
2017-10-26  7:41                                               ` Michal Hocko
2017-10-20  7:22                               ` Xishi Qiu
2017-10-20  8:17                                 ` Michal Hocko
2017-10-23  5:26                                   ` Joonsoo Kim
2017-10-26 13:04                             ` Vlastimil Babka
2017-10-26 13:59                             ` Michal Hocko
2017-09-18  7:08 ` [PATCH 2/2] mm, memory_hotplug: remove timeout from __offline_memory Michal Hocko
  -- strict thread matches above, loose matches on Subject: below --
2017-09-04  8:21 [PATCH 0/2] mm, memory_hotplug: redefine memory offline retry logic Michal Hocko
2017-09-04  8:21 ` [PATCH 1/2] mm, memory_hotplug: do not fail offlining too early Michal Hocko
2017-09-05  6:29   ` Anshuman Khandual
2017-09-05  7:13     ` Michal Hocko
2017-09-08 17:26   ` Vlastimil Babka
2017-09-11  8:17     ` Michal Hocko
2017-09-13 11:41       ` Vlastimil Babka
2017-09-13 12:10         ` Michal Hocko
2017-09-13 12:14           ` Michal Hocko
2017-09-13 12:19             ` Vlastimil Babka
2017-09-13 12:32               ` Michal Hocko

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