Ok, I did more testing. Qu is right that btrfs check does not crash the kernel.
It just takes all the memory until linux hangs everywhere, and somehow (no idea
why)
the OOM killer never triggers.
Details below:
On Tue, Jul 17, 2018 at 01:32:57PM -0700, Marc MERLIN wrote:
> Here is what I got when the system was not doing well (it took minutes to
> run):
>
> total used free shared buffers cached
> Mem: 32643788 32070952 572836 0 102160 4378772
> -/+ buffers/cache: 27590020 5053768
> Swap: 15616764 973596 14643168
ok, the reason it was not that close to 0 was due to /dev/shm it seems.
I cleared that, and now I can get it to go to near 0 again.
I'm wrong about the system being fully crashed, it's not, it's just very
close to being hung.
I can type killall -9 btrfs in the serial console and wait a few minutes.
The system eventually recovers, but it's impossible to fix anything via ssh
apparently because networking does not get to run when I'm in this state.
I'm not sure why my system reproduces this easy while Qu's system does not,
but Qu was right that the kernel is not dead and that it's merely a problem of
userspace
taking all the RAM and somehow not being killed by OOM
I checked the PID and don't see why it's not being killed:
gargamel:/proc/31006# grep . oom*
oom_adj:0
oom_score:221 << this increases a lot, but OOM never kills it
oom_score_adj:0
I have these variables:
/proc/sys/vm/oom_dump_tasks:1
/proc/sys/vm/oom_kill_allocating_task:0
/proc/sys/vm/overcommit_kbytes:0
/proc/sys/vm/overcommit_memory:0
/proc/sys/vm/overcommit_ratio:50 << is this bad (seems default)
Here is my system when it virtually died:
ER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 31006 21.2 90.7 29639020 29623180 pts/19 D+ 13:49 1:35 ./btrfs check
/dev/mapper/dshelf2
total used free shared buffers cached
Mem: 32643788 32180100 463688 0 44664 119508
-/+ buffers/cache: 32015928 627860
Swap: 15616764 443676 15173088
MemTotal: 32643788 kB
MemFree: 463440 kB
MemAvailable: 44864 kB
Buffers: 44664 kB
Cached: 120360 kB
SwapCached: 87064 kB
Active: 30381404 kB
Inactive: 585952 kB
Active(anon): 30334696 kB
Inactive(anon): 474624 kB
Active(file): 46708 kB
Inactive(file): 111328 kB
Unevictable: 5616 kB
Mlocked: 5616 kB
SwapTotal: 15616764 kB
SwapFree: 15173088 kB
Dirty: 1636 kB
Writeback: 4 kB
AnonPages: 30734240 kB
Mapped: 67236 kB
Shmem: 3036 kB
Slab: 267884 kB
SReclaimable: 51528 kB
SUnreclaim: 216356 kB
KernelStack: 10144 kB
PageTables: 69284 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 31938656 kB
Committed_AS: 32865492 kB
VmallocTotal: 34359738367 kB
VmallocUsed: 0 kB
VmallocChunk: 0 kB
HardwareCorrupted: 0 kB
AnonHugePages: 0 kB
ShmemHugePages: 0 kB
ShmemPmdMapped: 0 kB
CmaTotal: 16384 kB
CmaFree: 0 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB
Hugetlb: 0 kB
DirectMap4k: 560404 kB
DirectMap2M: 32692224 kB
--
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems ....
.... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/
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