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[91.12.102.202]) by smtp.gmail.com with ESMTPSA id q20sm19456718wrf.45.2021.06.14.00.38.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 14 Jun 2021 00:38:16 -0700 (PDT) To: Hillf Danton , Nathan Chancellor Cc: "K. Y. Srinivasan" , Haiyang Zhang , Stephen Hemminger , Wei Liu , Dexuan Cui , linux-hyperv@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Oscar Salvador References: <20210612021115.2136-1-hdanton@sina.com> From: David Hildenbrand Organization: Red Hat Subject: Re: vmemmap alloc failure in hot_add_req() Message-ID: <951ddbaf-3d74-7043-4866-3809ff991cfd@redhat.com> Date: Mon, 14 Jun 2021 09:38:15 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: <20210612021115.2136-1-hdanton@sina.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12.06.21 04:11, Hillf Danton wrote: > On Fri, 11 Jun 2021 12:48:26 -0700 Nathan Chancellor wrote: >> Hi all, >> >> I am occasionally seeing a kernel warning when running virtual machines >> in Hyper-V, which usually happens a minute or so after boot. It does not >> happen on every boot and it is reproducible on at least v5.10. I think >> it might have something to do with constant reboots, which I do when >> testing various kernels. >> >> The stack trace is as follows: >> >> [ 49.215291] kworker/0:1: vmemmap alloc failure: order:9, mode:0x4cc0(GFP_KERNEL|__GFP_RETRY_MAYFAIL), nodemask=(null),cpuset=/,mems_allowed=0 >> [ 49.215299] CPU: 0 PID: 18 Comm: kworker/0:1 Not tainted 5.13.0-rc5 #1 >> [ 49.215301] Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS Hyper-V UEFI Release v4.0 11/01/2019 >> [ 49.215302] Workqueue: events hot_add_req [hv_balloon] > > Apart from order:9 (mm Cced), events_unbound is the right workqueue instead > because the report shows the risk that hot_add_req could block other pending > events longer than thought. Any special reason for the events wq? > >> [ 49.215307] Call Trace: >> [ 49.215310] dump_stack+0x76/0x94 >> [ 49.215314] warn_alloc.cold+0x78/0xdc >> [ 49.215316] ? __alloc_pages+0x200/0x230 >> [ 49.215319] vmemmap_alloc_block+0x86/0xdc >> [ 49.215323] vmemmap_populate+0x10e/0x31c >> [ 49.215324] __populate_section_memmap+0x38/0x4e >> [ 49.215326] sparse_add_section+0x12c/0x1cf >> [ 49.215329] __add_pages+0xa9/0x130 >> [ 49.215330] add_pages+0x12/0x60 >> [ 49.215333] add_memory_resource+0x180/0x300 >> [ 49.215335] __add_memory+0x3b/0x80 >> [ 49.215336] add_memory+0x2e/0x50 >> [ 49.215337] hot_add_req+0x3fc/0x5a0 [hv_balloon] >> [ 49.215340] process_one_work+0x214/0x3e0 >> [ 49.215342] worker_thread+0x4d/0x3d0 >> [ 49.215344] ? process_one_work+0x3e0/0x3e0 >> [ 49.215345] kthread+0x133/0x150 >> [ 49.215347] ? kthread_associate_blkcg+0xc0/0xc0 >> [ 49.215348] ret_from_fork+0x22/0x30 >> [ 49.215351] Mem-Info: >> [ 49.215352] active_anon:251 inactive_anon:140868 isolated_anon:0 >> active_file:47497 inactive_file:88505 isolated_file:0 >> unevictable:8 dirty:14 writeback:0 >> slab_reclaimable:12013 slab_unreclaimable:11403 >> mapped:131701 shmem:12671 pagetables:3140 bounce:0 >> free:41388 free_pcp:37 free_cma:0 >> [ 49.215355] Node 0 active_anon:1004kB inactive_anon:563472kB active_file:189988kB inactive_file:354020kB unevictable:32kB isolated(anon):0kB isolated(file):0kB mapped:526804kB dirty:56kB writeback:0kB shmem:50684kB shmem_thp: 0kB shmem_pmdmapped: 0kB anon_thp: 0kB writeback_tmp:0kB kernel_stack:5904kB pagetables:12560kB all_unreclaimable? no >> [ 49.215358] Node 0 DMA free:6496kB min:480kB low:600kB high:720kB reserved_highatomic:0KB active_anon:0kB inactive_anon:3120kB active_file:2584kB inactive_file:2792kB unevictable:0kB writepending:0kB present:15996kB managed:15360kB mlocked:0kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB >> [ 49.215361] lowmem_reserve[]: 0 1384 1384 1384 1384 >> [ 49.215364] Node 0 DMA32 free:159056kB min:44572kB low:55712kB high:66852kB reserved_highatomic:0KB active_anon:1004kB inactive_anon:560352kB active_file:187004kB inactive_file:350864kB unevictable:32kB writepending:56kB present:1555760kB managed:1432388kB mlocked:32kB bounce:0kB free_pcp:172kB local_pcp:0kB free_cma:0kB >> [ 49.215367] lowmem_reserve[]: 0 0 0 0 0 >> [ 49.215369] Node 0 DMA: 17*4kB (UM) 13*8kB (M) 10*16kB (M) 3*32kB (ME) 3*64kB (UME) 4*128kB (UME) 1*256kB (E) 2*512kB (UE) 2*1024kB (ME) 1*2048kB (E) 0*4096kB = 6508kB >> [ 49.215377] Node 0 DMA32: 8061*4kB (UME) 5892*8kB (UME) 2449*16kB (UME) 604*32kB (UME) 207*64kB (UME) 49*128kB (UM) 7*256kB (M) 1*512kB (M) 0*1024kB 0*2048kB 0*4096kB = 159716kB >> [ 49.215388] 148696 total pagecache pages >> [ 49.215388] 0 pages in swap cache >> [ 49.215389] Swap cache stats: add 0, delete 0, find 0/0 >> [ 49.215390] Free swap = 0kB >> [ 49.215390] Total swap = 0kB >> [ 49.215391] 392939 pages RAM >> [ 49.215391] 0 pages HighMem/MovableOnly >> [ 49.215391] 31002 pages reserved >> [ 49.215392] 0 pages cma reserved >> [ 49.215393] 0 pages hwpoisoned >> >> Is this a known issue and/or am I doing something wrong? I only noticed >> this because there are times when I am compiling something intensive in >> the VM such as LLVM and the VM runs out of memory even though I have >> plenty of free memory on the host but I am not sure if this warning is >> related to that issue. Hi, Is hotplugged memory getting onlined automatically (either from user space via a udev script or via the kernel, for example, with CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE)? If it's not getting onlined, you easily sport after hotplug e.g., via "lsmem" that there are quite some offline memory blocks. Note that x86_64 code will fallback from populating huge pages to populating base pages for the vmemmap; this can happen easily when under memory pressure. If adding memory would fail completely, you'd see another "hot_add memory failed error is ..." error message from hyper-v in the kernel log. If that doesn't show up, it's simply suboptimal, but hotplugging memory still succeeded. Note: we could support "memmap_on_memory" in some cases (e.g., no memory holes in hotadded range) when hotplugging memory blocks via hyper-v, which would result in this warning less trigger less frequently. -- Thanks, David / dhildenb