Tracing large binary allocations

[Lukas Larsson]

Hello,

On Tue, Apr 7, 2020 at 9:26 AM Devon Estes <devon.c.estes@REDACTED> wrote:

> Hi all,
>
> I’m seeing some cases in my application where our off-process binary heap
> allocation jumps by several orders of magnitude and then goes down right
> after. I’m sure this is something that’s in our app just loading dozens of
> huge binaries into memory at once and not a bug in anything underlying or a
> binary leak, but finding where these allocations are happening so I can
> make some changes to avoid this has so far not yielded any results. Ideally
> I’d like to be able to set a trace with something like erlang:trace/3 on
> some function that sends a tracer message whenever a binary over 30MB is
> allocated and includes the call stack or even just the calling function
> that allocated the binary in the trace message.
>

> Going through the binary vheap and getting a list of the processes that
> have references to those binaries won’t help in this case.
>
> Is such a trace possible? Is there some flag I can set when starting my
> BEAM process to give me some kind of debug output that would give me this
> information? I’d imagine this is all in C, so it might be a bit tricky...
>

No it is not possible without modifying the VM. I can't think of any good
way to get this information without scanning the process' vheap, which as
you say would not help much in this case.


> Thanks in advance for the help!
>
> Cheers,
> Devon
> --
>
> _________________
> Devon Estes
> 203.559.0323
> www.devonestes.com
>
>
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