Comment 0 for bug 1756129

Issue description: Memory demand increases very fast up to the maximum available memory, call traces show up in /var/log/syslog, the VM becomes unresponsive during the memory consumption, but it becomes responsive right after stress-ng ends its execution, therefore we can say the issue might be in the Dynamic Memory feature.

Platform: host independent

Distribution name and release:
 - Bionic (4.15.0-10-generic)
 - Linux Azure kernel (4.13.0-1012-azure)

Repro rate: 100%

VM configuration:
 Kernel: 4.13.0-1012-azure
 CPU: 8 cores
 RAM: 2048 MB
 Enable Dynamic Memory: Yes
 Minimum RAM: 512 MB
 Maximum RAM: 8192 MB
 Memory buffer: 20%
 Memory weight: 100%

Repro steps:
 1. Start the VM with the above configuration.
 2. Run stress-ng with the following parameters:
  stress-ng -m 16 -vm-bytes 256M -t 200 --backoff 10000000
 3. In less than 60 seconds the entire memory is consumed.

Additional info:
 1. We also tested this on Xenial with default kernel and the issue does not occur.
 2. The call trace message from syslog can be seen below.

 Mar 14 08:42:17 xenial kernel: [ 257.120261] Call Trace:
Mar 14 08:42:17 xenial kernel: [ 257.120267] dump_stack+0x63/0x82
Mar 14 08:42:17 xenial kernel: [ 257.120271] dump_header+0x97/0x225
Mar 14 08:42:17 xenial kernel: [ 257.120276] ? security_capable_noaudit+0x4b/0x70
Mar 14 08:42:17 xenial kernel: [ 257.120277] oom_kill_process+0x219/0x420
Mar 14 08:42:17 xenial kernel: [ 257.120279] out_of_memory+0x11d/0x4b0
Mar 14 08:42:17 xenial kernel: [ 257.120282] __alloc_pages_slowpath+0xd32/0xe10
Mar 14 08:42:17 xenial kernel: [ 257.120284] __alloc_pages_nodemask+0x263/0x280
Mar 14 08:42:17 xenial kernel: [ 257.120289] alloc_pages_vma+0x88/0x1e0
Mar 14 08:42:17 xenial kernel: [ 257.120292] shmem_alloc_page+0x70/0xc0
Mar 14 08:42:17 xenial kernel: [ 257.120295] ? __radix_tree_insert+0x45/0x230
Mar 14 08:42:17 xenial kernel: [ 257.120297] shmem_alloc_and_acct_page+0x73/0x1b0
Mar 14 08:42:17 xenial kernel: [ 257.120298] ? find_get_entry+0x1e/0xe0
Mar 14 08:42:17 xenial kernel: [ 257.120300] shmem_getpage_gfp+0x18f/0xbf0
Mar 14 08:42:17 xenial kernel: [ 257.120303] shmem_fault+0x9d/0x1e0
Mar 14 08:42:17 xenial kernel: [ 257.120306] ? file_update_time+0x60/0x110
Mar 14 08:42:17 xenial kernel: [ 257.120309] __do_fault+0x24/0xd0
Mar 14 08:42:17 xenial kernel: [ 257.120311] __handle_mm_fault+0x983/0x1080
Mar 14 08:42:17 xenial kernel: [ 257.120314] ? set_next_entity+0xd9/0x220
Mar 14 08:42:17 xenial kernel: [ 257.120316] handle_mm_fault+0xcc/0x1c0
Mar 14 08:42:17 xenial kernel: [ 257.120319] __do_page_fault+0x258/0x4f0
Mar 14 08:42:17 xenial kernel: [ 257.120320] do_page_fault+0x22/0x30
Mar 14 08:42:17 xenial kernel: [ 257.120323] ? page_fault+0x36/0x60
Mar 14 08:42:17 xenial kernel: [ 257.120325] page_fault+0x4c/0x60
Mar 14 08:42:17 xenial kernel: [ 257.120327] RIP: 0033:0x4493ad
Mar 14 08:42:17 xenial kernel: [ 257.120328] RSP: 002b:00007ffd3ff927b0 EFLAGS: 00010286
Mar 14 08:42:17 xenial kernel: [ 257.120329] RAX: 00000000c6a6a9e7 RBX: 00000001a8ae9d07 RCX: 0000000021b83c00
Mar 14 08:42:17 xenial kernel: [ 257.120330] RDX: 00007f2ad911d000 RSI: 00000000271ea9e7 RDI: 00000000271e9660
Mar 14 08:42:17 xenial kernel: [ 257.120331] RBP: 00007f2adab70000 R08: 000000001bda3103 R09: 0000000048373eca
Mar 14 08:42:17 xenial kernel: [ 257.120331] R10: 0000000048373eca R11: 00007f2acab70000 R12: 0000000000000000
Mar 14 08:42:17 xenial kernel: [ 257.120332] R13: 8309310348373eca R14: 56b63c1fe6166568 R15: 00007f2acab70000
Mar 14 08:42:17 xenial kernel: [ 257.120333] Mem-Info:
Mar 14 08:42:17 xenial kernel: [ 257.120337] active_anon:249563 inactive_anon:83607 isolated_anon:65
Mar 14 08:42:17 xenial kernel: [ 257.120337] active_file:54 inactive_file:74 isolated_file:0
Mar 14 08:42:17 xenial kernel: [ 257.120337] unevictable:2561 dirty:0 writeback:68 unstable:0
Mar 14 08:42:17 xenial kernel: [ 257.120337] slab_reclaimable:10707 slab_unreclaimable:16622
Mar 14 08:42:17 xenial kernel: [ 257.120337] mapped:132260 shmem:332303 pagetables:2888 bounce:0
Mar 14 08:42:17 xenial kernel: [ 257.120337] free:12983 free_pcp:493 free_cma:0
Mar 14 08:42:17 xenial kernel: [ 257.120340] Node 0 active_anon:998252kB inactive_anon:334428kB active_file:216kB inactive_file:296kB unevictable:10244kB isolated(anon):260kB isolated(file):0kB mapped:529040kB dirty:0kB writeback:272kB shmem:1329212kB shmem_thp: 0kB shmem_pmdmapped: 0kB anon_thp: 0kB writeback_tmp:0kB unstable:0kB all_unreclaimable? no
Mar 14 08:42:17 xenial kernel: [ 257.120341] Node 0 DMA free:7404kB min:392kB low:488kB high:584kB active_anon:5616kB inactive_anon:2384kB active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB present:15992kB managed:15908kB mlocked:0kB kernel_stack:0kB pagetables:64kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB
Mar 14 08:42:17 xenial kernel: [ 257.120345] lowmem_reserve[]: 0 1754 1754 1754 1754
Mar 14 08:42:17 xenial kernel: [ 257.120347] Node 0 DMA32 free:44528kB min:44660kB low:55824kB high:66988kB active_anon:992772kB inactive_anon:331896kB active_file:216kB inactive_file:296kB unevictable:10244kB writepending:600kB present:2080704kB managed:1818152kB mlocked:10244kB kernel_stack:4512kB pagetables:11488kB bounce:0kB free_pcp:1972kB local_pcp:236kB free_cma:0kB
Mar 14 08:42:17 xenial kernel: [ 257.120351] lowmem_reserve[]: 0 0 0 0 0
Mar 14 08:42:17 xenial kernel: [ 257.120353] Node 0 DMA: 1*4kB (U) 9*8kB (UME) 10*16kB (UME) 4*32kB (UM) 4*64kB (UM) 5*128kB (UME) 4*256kB (UM) 2*512kB (ME) 2*1024kB (ME) 1*2048kB (E) 0*4096kB = 7404kB
Mar 14 08:42:17 xenial kernel: [ 257.120363] Node 0 DMA32: 12*4kB (UME) 175*8kB (UE) 138*16kB (UE) 91*32kB (UM) 27*64kB (UM) 49*128kB (UM) 19*256kB (UM) 8*512kB (M) 21*1024kB (M) 0*2048kB 0*4096kB = 45032kB