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[Bug 1496317] Re: kexec fails with OOM killer with the current crashkernel=128 value


** Also affects: kexec-tools (Ubuntu Wily)
   Importance: Undecided
       Status: New

** Changed in: kexec-tools (Ubuntu Wily)
       Status: New => In Progress

** Changed in: kexec-tools (Ubuntu Wily)
     Assignee: (unassigned) => Louis Bouchard (louis-bouchard)

** Changed in: kexec-tools (Ubuntu Wily)
   Importance: Undecided => High

** Changed in: kexec-tools (Ubuntu)
       Status: In Progress => Fix Released

** Changed in: kexec-tools (Ubuntu)
     Assignee: Louis Bouchard (louis-bouchard) => (unassigned)

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  kexec fails with OOM killer with the current crashkernel=128 value

Status in kexec-tools package in Ubuntu:
  Fix Released
Status in kexec-tools source package in Wily:
  In Progress

Bug description:
  [SRU justification]
  This modification is required to fix memory shortage in the kexec booted kernel that blocks the creation of kernel crash dumps

  Without this fix, the kernel crash dump mechanism is unusable without applying a workaround

  Implement use of smaller initrd.img files located in /var/lib/kdump and used with the definition of KDUMP_KERNEL / KDUMP_INITRD in the config file.

  [Test Case]
  - Create a system running the standard Wily release
  - install the linux-crashdump metapackage
  - Enable the kdump mechanism by setting USE_KDUMP=1 in /etc/default/kdump-tools
  - Reboot to activate the crashkernel= kernel variable
  - execute the following as root to trigger a kernel crash :
    echo c > /proc/sysrq-trigger

  Without the fix, the kernel crash dump procedure will not complete
  (see Original description) and will be stopped by the OOM killer.

  With the fix, the kernel crash dump procedure will complete normally.

  This is a new implementation, taken from upstream's 1.5.9 version. In the eventuality that the package is installed without using the new variable definitions in /etc/default/kdump-tools, the old method will be used and will lead to the original failure.

  [Original description of the problem]
  With a very basic Wily image, just trigger a crash with sysrq-trigger after installing and setting up linux-crashdump and the kexec will fail with the following :

  [    0.334592] Trying to unpack rootfs image as initramfs...
  [    0.649440] swapper/0 invoked oom-killer: gfp_mask=0x200d2, order=0, oom_score_adj=0
  [    0.650332] swapper/0 cpuset=/ mems_allowed=0
  [    0.650856] CPU: 0 PID: 1 Comm: swapper/0 Tainted: G        W       4.2.0-7-generic #7-Ubuntu
  [    0.651788] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
  [    0.652691]  ffff88002fd906c8 ffff88002fcf76a8 ffffffff817b0465 000000000000000f
  [    0.653556]  ffff88002fd90000 ffff88002fcf7738 ffffffff817ae2b5 ffff88002ffc0e28
  [    0.654418]  ffff880033c164c0 ffff880033c16530 ffff88002fd90068 ffff88002fcf7748
  [    0.682339] Mem-Info:                                                                                 [756/1897]
  [    0.682599] active_anon:0 inactive_anon:0 isolated_anon:0
  [    0.682599]  active_file:2023 inactive_file:0 isolated_file:0
  [    0.682599]  unevictable:14845 dirty:0 writeback:0 unstable:0
  [    0.682599]  slab_reclaimable:1722 slab_unreclaimable:632
  [    0.682599]  mapped:0 shmem:0 pagetables:0 bounce:0
  [    0.682599]  free:0 free_pcp:2 free_cma:0
  [    0.685982] Node 0 DMA free:0kB min:0kB low:0kB high:0kB active_anon:0kB inactive_anon:0kB active_file:0kB inact
  ive_file:0kB unevictable:540kB isolated(anon):0kB isolated(file):0kB present:632kB managed:548kB mlocked:0kB dirty:
  0kB writeback:0kB mapped:0kB shmem:0kB slab_reclaimable:8kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:0kB
  unstable:0kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:540 all_unreclaimab
  le? yes
  [    0.690450] lowmem_reserve[]: 0 0 0 0
  [    0.690928] Node 0 DMA32 free:0kB min:0kB low:0kB high:0kB active_anon:0kB inactive_anon:0kB active_file:8092kB
  inactive_file:0kB unevictable:58840kB isolated(anon):0kB isolated(file):0kB present:130420kB managed:78064kB mlocke
  d:0kB dirty:0kB writeback:0kB mapped:0kB shmem:0kB slab_reclaimable:6880kB slab_unreclaimable:2528kB kernel_stack:4
  64kB pagetables:0kB unstable:0kB bounce:0kB free_pcp:8kB local_pcp:8kB free_cma:0kB writeback_tmp:0kB pages_scanned
  :58840 all_unreclaimable? yes
  [    0.695547] lowmem_reserve[]: 0 0 0 0
  [    0.696049] Node 0 DMA: 0*4kB 0*8kB 0*16kB 0*32kB 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 0k
  [    0.697335] Node 0 DMA32: 0*4kB 0*8kB 0*16kB 0*32kB 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB =
  [    0.698641] 16868 total pagecache pages
  [    0.699075] 0 pages in swap cache
  [    0.699448] Swap cache stats: add 0, delete 0, find 0/0
  [    0.700029] Free swap  = 0kB
  [    0.700356] Total swap = 0kB
  [    0.700679] 32763 pages RAM
  [    0.700991] 0 pages HighMem/MovableOnly
  [    0.701418] 13110 pages reserved
  [    0.701778] 0 pages cma reserved
  [    0.702139] 0 pages hwpoisoned
  [    0.702481] [ pid ]   uid  tgid total_vm      rss nr_ptes nr_pmds swapents oom_score_adj name
  [    0.703423] Kernel panic - not syncing: Out of memory and no killable processes...

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