[gpfsug-discuss] FS freeze on client nodes with nbCores>workerThreads

[CAPIT, NICOLAS]

Hello,

When the node is locked up there is no waiters ("mmdiad --waiters" or "mmfsadm dump waiters").
In the GPFS log file "/var/mmfs/gen/mmfslog" there is nothing and nothing in the dmesg output or system log.
The "mmgetstate" command says that the node is "active".
The only thing is the freeze of the FS.

Best regards,
Nicolas Capit
________________________________________
De : gpfsug-discuss-bounces at spectrumscale.org [gpfsug-discuss-bounces at spectrumscale.org] de la part de Aaron Knister [aaron.s.knister at nasa.gov]
Envoyé : mardi 27 juin 2017 01:57
À : gpfsug-discuss at spectrumscale.org
Objet : Re: [gpfsug-discuss] FS freeze on client nodes with nbCores>workerThreads

That's a fascinating bug. When the node is locked up what does "mmdiag
--waiters" show from the node in question? I suspect there's more
low-level diagnostic data that's helpful for the gurus at IBM but I'm
just curious what the waiters look like.

-Aaron

On 6/26/17 3:49 AM, CAPIT, NICOLAS wrote:
> Hello,
>
> I don't know if this behavior/bug was already reported on this ML, so in
> doubt.
>
> Context:
>
>    - SpectrumScale 4.2.2-3
>    - client node with 64 cores
>    - OS: RHEL7.3
>
> When a MPI job with 64 processes is launched on the node with 64 cores
> then the FS freezed (only the output log file of the MPI job is put on
> the GPFS; so it may be related to the 64 processes writing in a same
> file???).
>
>    strace -p 3105         # mmfsd pid stucked
>    Process 3105 attached
>    wait4(-1,              # stucked at this point
>
>    strace ls /gpfs
>    stat("/gpfs", {st_mode=S_IFDIR|0755, st_size=131072, ...}) = 0
>    openat(AT_FDCWD, "/gpfs", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC
> # stucked at this point
>
> I have no problem with the other nodes of 28 cores.
> The GPFS command mmgetstate is working and I am able to use mmshutdown
> to recover the node.
>
>
> If I put workerThreads=72 on the 64 core node then I am not able to
> reproduce the freeze and I get the right behavior.
>
> Is this a known bug with a number of cores > workerThreads?
>
> Best regards,
> --
> *Nicolas Capit*
>
>
> _______________________________________________
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>

--
Aaron Knister
NASA Center for Climate Simulation (Code 606.2)
Goddard Space Flight Center
(301) 286-2776
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