From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f72.google.com (mail-pg0-f72.google.com [74.125.83.72]) by kanga.kvack.org (Postfix) with ESMTP id 9C26E6B0253 for ; Tue, 10 Oct 2017 22:37:55 -0400 (EDT) Received: by mail-pg0-f72.google.com with SMTP id u23so999865pgo.7 for ; Tue, 10 Oct 2017 19:37:55 -0700 (PDT) Received: from ozlabs.org (ozlabs.org. [103.22.144.67]) by mx.google.com with ESMTPS id o15si2945041pgq.475.2017.10.10.19.37.53 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 10 Oct 2017 19:37:54 -0700 (PDT) From: Michael Ellerman Subject: Re: [PATCH 1/2] mm, memory_hotplug: do not fail offlining too early In-Reply-To: <20171010122726.6jrfdzkscwge6gez@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> Date: Wed, 11 Oct 2017 13:37:50 +1100 Message-ID: <87infmz9xd.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Andrew Morton , KAMEZAWA Hiroyuki , Reza Arbab , Yasuaki Ishimatsu , qiuxishi@huawei.com, Igor Mammedov , Vitaly Kuznetsov , linux-mm@kvack.org, LKML , Vlastimil Babka 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. > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 3badcedf96a7..00d042052501 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -7368,6 +7368,9 @@ 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 > > >> 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 > > I do not see how this is related to the offline path. It's blocked doing get_online_mems(). So it's unrelated to the offline, but it can't proceed until the offline finishes, which it never does, IIUIC. cheers -- 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