From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk1-f197.google.com (mail-qk1-f197.google.com [209.85.222.197]) by kanga.kvack.org (Postfix) with ESMTP id 40C086B0269 for ; Mon, 5 Nov 2018 04:26:27 -0500 (EST) Received: by mail-qk1-f197.google.com with SMTP id f22so19964411qkm.11 for ; Mon, 05 Nov 2018 01:26:27 -0800 (PST) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id u2si700293qtd.231.2018.11.05.01.26.23 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 05 Nov 2018 01:26:23 -0800 (PST) Date: Mon, 5 Nov 2018 17:26:18 +0800 From: Baoquan He Subject: Re: [PATCH] mm, memory_hotplug: teach has_unmovable_pages about of LRU migrateable pages Message-ID: <20181105092618.GI27491@MiWiFi-R3L-srv> References: <20181101091055.GA15166@MiWiFi-R3L-srv> <20181102155528.20358-1-mhocko@kernel.org> <20181105002009.GF27491@MiWiFi-R3L-srv> <20181105091407.GB4361@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181105091407.GB4361@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Andrew Morton , linux-mm@kvack.org, LKML , Stable tree On 11/05/18 at 10:14am, Michal Hocko wrote: > On Mon 05-11-18 08:20:09, Baoquan He wrote: > > Hi Michal, > > > > On 11/02/18 at 04:55pm, Michal Hocko wrote: > > > From: Michal Hocko > > > > > > Baoquan He has noticed that 15c30bc09085 ("mm, memory_hotplug: make > > > has_unmovable_pages more robust") is causing memory offlining failures > > > on a movable node. After a further debugging it turned out that > > > has_unmovable_pages fails prematurely because it stumbles over off-LRU > > > pages. Nevertheless those pages are not on LRU because they are waiting > > > on the pcp LRU caches (an example of __dump_page added by a debugging > > > patch) > > > [ 560.923297] page:ffffea043f39fa80 count:1 mapcount:0 mapping:ffff880e5dce1b59 index:0x7f6eec459 > > > [ 560.931967] flags: 0x5fffffc0080024(uptodate|active|swapbacked) > > > [ 560.937867] raw: 005fffffc0080024 dead000000000100 dead000000000200 ffff880e5dce1b59 > > > [ 560.945606] raw: 00000007f6eec459 0000000000000000 00000001ffffffff ffff880e43ae8000 > > > [ 560.953323] page dumped because: hotplug > > > [ 560.957238] page->mem_cgroup:ffff880e43ae8000 > > > [ 560.961620] has_unmovable_pages: pfn:0x10fd030d, found:0x1, count:0x0 > > > [ 560.968127] page:ffffea043f40c340 count:2 mapcount:0 mapping:ffff880e2f2d8628 index:0x0 > > > [ 560.976104] flags: 0x5fffffc0000006(referenced|uptodate) > > > [ 560.981401] raw: 005fffffc0000006 dead000000000100 dead000000000200 ffff880e2f2d8628 > > > [ 560.989119] raw: 0000000000000000 0000000000000000 00000002ffffffff ffff88010a8f5000 > > > [ 560.996833] page dumped because: hotplug > > > > Sorry, last week I didn't test this patch with memory pressure adding. > > Today use "stress -m 200 -t 2h" to add pressure, hot removing failed. > > Will send you output log. W/o memory pressure, it sometimes succeed. I > > saw one failure last night, it still show un-removable as 0 in > > hotpluggable node one time, I worried it might be caused by my compiling > > mistake, so compile and try again this morning. > > In a private email you have sent this (let's assume this is correctly > testing the patch I have posted): Yeah, I recompiled and copy bzImage to /boot to ensure the patch is compiled in. > > : [43283.914082] has_unmovable_pages: pfn:0x10e62600, found:0x1, count:0x0 > : [43283.920669] page:ffffea0439898000 count:1 mapcount:1 mapping:ffff880e5639d3c9 index:0x7f2430400 compound_mapcount: 1 > : [43283.931219] flags: 0x5fffffc0090034(uptodate|lru|active|head|swapbacked) > : [43283.937954] raw: 005fffffc0090034 ffffea043ffcb888 ffffea043f728008 ffff880e5639d3c9 > : [43283.945722] raw: 00000007f2430400 0000000000000000 00000001ffffffff ffff880e2baad000 > : [43283.955381] page dumped because: hotplug > > The page is both LRU and SwapBacked which should hit the some of the > checks in has_unmovable_pages. The fact it hasn't means we have clearly > raced with the page being allocated and marked SwapBacked/LRU. This is > surely possible and there is no universal way to prevent from that for > all types of potentially migratedable pages. The race window should be > relatively small. Maybe we can add a retry for movable zone pages. > > How reproducible this is? On the bare metal with 8 nodes and each node has 64 GB memory, node1~7 are hotpluggable and movable_node is added. After reboot, execute "stress -m 200 -t 2h", by default the 200 processes will malloc/free 256MB continuously. Then hot remove one memory board on node1~7, it always happened. The progress is that all memory blocks on node1~7 are removable now, accessing and reading them won't trigger the old trace now. > > But, as I've said memory isolation resp. has_unmovable_pages begs for a > complete redesign. So how about using the patch I pasted before? It has an explanation and test result is good. diff --git a/mm/page_alloc.c b/mm/page_alloc.c index a919ba5..021e39d 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -7824,7 +7824,8 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, if (__PageMovable(page)) continue; - if (!PageLRU(page)) + if (!PageLRU(page) && + (get_pageblock_migratetype(page) != MIGRATE_MOVABLE)) found++; /* * If there are RECLAIMABLE pages, we need to check Thanks Baoquan