[erlang-questions] compile:forms is sometimes slow

Roger Lipscombe roger@REDACTED
Mon Nov 10 16:50:45 CET 2014

I'm using 'meck' in my unit tests, and -- on a particular machine, of
which more later -- it's slow, sometimes.

It appears to be impossible to tell eunit (via rebar) to relax its 5
second timeout, without annotating every test and fixture (which I
don't want to do), so I'm trying to figure out why it's so slow.

I've tracked down the slowness, and it appears to be in
compile:forms/2. Usually, it takes around 2-3ms, but occasionally, it
takes ~6 seconds.

Any ideas why?

Oh, the machine? It's a VirtualBox VM, 2GB RAM, 6 cores, VMDK is on an
SSD. It's noticeably slower than the host, but not painfully so. It
seems like the performance just drops off a cliff under certain


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