From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756099AbdJJMFM (ORCPT ); Tue, 10 Oct 2017 08:05:12 -0400 Received: from ozlabs.org ([103.22.144.67]:54837 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755866AbdJJMFL (ORCPT ); Tue, 10 Oct 2017 08:05:11 -0400 From: Michael Ellerman To: Michal Hocko , Andrew Morton Cc: KAMEZAWA Hiroyuki , Reza Arbab , Yasuaki Ishimatsu , qiuxishi@huawei.com, Igor Mammedov , Vitaly Kuznetsov , linux-mm@kvack.org, LKML , Michal Hocko , Vlastimil Babka Subject: Re: [PATCH 1/2] mm, memory_hotplug: do not fail offlining too early In-Reply-To: <20170918070834.13083-2-mhocko@kernel.org> References: <20170918070834.13083-1-mhocko@kernel.org> <20170918070834.13083-2-mhocko@kernel.org> Date: Tue, 10 Oct 2017 23:05:08 +1100 Message-ID: <87bmlfw6mj.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 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. With commit 3aa2823fdf66 ("mm, memory_hotplug: remove timeout from __offline_memory") also applied, it appears to just get stuck forever, and I get lots of: [ 1232.112953] INFO: task kworker/3:0:4609 blocked for more than 120 seconds. [ 1232.113067] Not tainted 4.14.0-rc4-gcc6-next-20171009-g49827b9 #1 [ 1232.113183] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 1232.113319] kworker/3:0 D11984 4609 2 0x00000800 [ 1232.113416] Workqueue: memcg_kmem_cache memcg_kmem_cache_create_func [ 1232.113531] Call Trace: [ 1232.113579] [c0000000fb2db7a0] [c0000000fb2db900] 0xc0000000fb2db900 (unreliable) [ 1232.113717] [c0000000fb2db970] [c00000000001c964] __switch_to+0x304/0x6e0 [ 1232.113840] [c0000000fb2dba10] [c000000000a408c0] __schedule+0x2e0/0xa80 [ 1232.113978] [c0000000fb2dbae0] [c000000000a410a8] schedule+0x48/0xc0 [ 1232.114113] [c0000000fb2dbb10] [c000000000a44d88] rwsem_down_read_failed+0x128/0x1b0 [ 1232.114269] [c0000000fb2dbb70] [c0000000001696a8] __percpu_down_read+0x108/0x110 [ 1232.114426] [c0000000fb2dbba0] [c00000000032e498] get_online_mems+0x68/0x80 [ 1232.115487] [c0000000fb2dbbc0] [c0000000002c82ec] memcg_create_kmem_cache+0x4c/0x190 [ 1232.115651] [c0000000fb2dbc60] [c0000000003483b8] memcg_kmem_cache_create_func+0x38/0xf0 [ 1232.115809] [c0000000fb2dbc90] [c000000000121594] process_one_work+0x2b4/0x590 [ 1232.115964] [c0000000fb2dbd20] [c000000000121908] worker_thread+0x98/0x5d0 [ 1232.116095] [c0000000fb2dbdc0] [c00000000012a134] kthread+0x164/0x1b0 [ 1232.116229] [c0000000fb2dbe30] [c00000000000bae0] ret_from_kernel_thread+0x5c/0x7c cheers