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<p>It's linux (ubuntu). I read /proc/[pid]/statm, take RSS number of
pages (the 2nd value in the line of that file) and calculate
memory used by Erlang VM as RSS x page size (read as "getconf
PAGESIZE").<br>
</p>
<div class="moz-cite-prefix">On 31.01.2020 19:59, Jesper Louis
Andersen wrote:<br>
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cite="mid:CAGrdgiWO=rhZ5iC6vVV+N1xt67nPwH=Lr4het9te=yBLCrZtXw@mail.gmail.com">
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<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif">When you say
/proc/pid, what are you looking at specifically in there? It
is a bit different depending on which Unix you run on, so a
simple example will help a lot.</div>
<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif"><br>
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<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif">In particular,
my early guess is going to be virtual memory vs physical RSS
mapping. The former can be much higher than the latter.
Especially in system such as Linux, which allow overcommitting
memory.</div>
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<br>
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<div dir="ltr" class="gmail_attr">On Fri, Jan 31, 2020 at 7:22
PM Vyacheslav Levytskyy <<a
href="mailto:v.levytskyy@yahoo.com" moz-do-not-send="true">v.levytskyy@yahoo.com</a>>
wrote:<br>
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<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hello,<br>
<br>
I wonder why memory used by Erlang VM as reported by the
kernel via the <br>
/proc/pid differs from erlang:memory(total). In my current
configuration <br>
I observe realistic response from erlang:memory(total) and
much lower <br>
values from the /proc/pid.<br>
<br>
I'm not surprised by the difference itself, but rather by the
fact that <br>
the /proc/pid gives unrealistically lower values -- I'm not
100% sure, <br>
but it looks like RabbitMQ is using the /proc/pid approach by
default, <br>
proposing also recon_alloc:memory(allocated) and
erlang:memory(total) as <br>
available options of Erlang VM memory consumption calculation
strategy.<br>
<br>
Does anybody have insights of what and why is going on with
those <br>
calculations of memory used by Erlang VM? Is it possible to
select one <br>
strategy beforehand for my Erlang app, or I must measure on
each new <br>
configuration what looks more precise? Should I compare and
change the <br>
strategy during run-time, or after I selected a strategy once
for my <br>
configuration I can be sure that selected approach always
better than <br>
other two?<br>
<br>
Thank you,<br>
Vyacheslav<br>
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-- <br>
<div dir="ltr" class="gmail_signature">J.</div>
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