Re: Calculating mem requirements for parallel queries and Docker and coredumps!

The --shm-size flag is available in docker run cli. Using k8s mount an
emptyDir to /dev/shm and set the medium as Memory.

Peter Tormey

ptormey(at)sofi(dot)org

On Mon, Feb 11, 2019 at 10:31 AM Jorge Torralba <jorge(dot)torralba(at)gmail(dot)com>
wrote:

> So this weekend we ran into the the docker limit of 64m for /dev/shm in
> one of our highest volume db's in production which we just upgraded to 11
> from 9.5. The typical ERROR: could not resize shared memory segment ....
> was flooding our log files and we were core dumping constantly. We had to
> set max_parallel_workers_per = 0 in order to disable the feature. This
> resolved the problem but . took away a feature were looking forward to use.
>
> Our system is 44 cores with 300 gigs of ram, 75 gig shared_buffers, 250mb
> work_mem and 600 max _connections although we use 270 consistent connection
> remainders are for redeploy that consume additional connections while
> others expire.
>
> Having said all this, the parallel query options where all default values
> and we were brought to our knees.
>
> So, I cannot find any documentation anywhere that would help me calculate
> the size for shm_size and have docker started with that value. Are there
> any tios or formula to help with this ?
>
> Lastly, is there a way to turn off postgres core dump on segfaults ? Every
> time we generated the could not resize error, it generated a core dump
> which killed IO on the system.
>
> Thanks
>
>
> Thanks,
>
> Jorge Torralba
> ----------------------------
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