Discrepancy between OS memory and erlang virtual memory?

Dominic Letz dominic@REDACTED
Thu Sep 23 09:13:29 CEST 2021


The erlang vm has it's own memory allocators (carriers) they usually create
a small memory overhead. I've seen them consuming exorbitant amounts of
memory before, likely because of memory fragmentation. Their usage is not
reported in the erlang virtual memory stats by default but you can check
them explicitly.

When fighting with memory fragmentation I created this script to show the
current carrier overhead: (waste)
https://gist.github.com/dominicletz/615e4b89b9e6f2059b2520ed9adac5dc

My solution in the end was to upgrade OTP to a newer version. And it made
the crazy overheads go away.

 Cheers!

Max Lapshin <max.lapshin@REDACTED> schrieb am Do., 23. Sep. 2021, 08:42:

> You show a strange graphic without any numbers. all other commands are
> also cutted.
>
> Also part of your email is rather unclear: you write to a public list that
> your email is confidential. Bad idea.
>
> About memory:
>
> 1) use recon in your production. recon_alloc will help to collect big
> amount of information from erlang runtime
> 2) take a look at /proc/3975367/maps, sometimes it helps to find leaks or
> better interpret numbers.
>
> What you see is a mismatch between different ways to calculate memory.
> Usually it is ok to live with such a difference.
>
>
>
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