Virtual Memory Usage

Ben Somers somers.ben at
Thu Nov 10 18:07:51 EST 2011


I've been testing unicorn as a replacement for passenger in my
company's Rails apps, and generally am very much liking it, and will
probably go through with the switch (our deployment times are killing
us). I've been running tests on with jmeter against a demo EC2
m1.xlarge running Ubuntu 9.10 (yes, we know it's out od date), with
15GB RAM, 4x2GHz CPU.

The server is behaving fine, with most of the unicorn workers sitting
at about 280MB resident memory, comparable to passenger's workers. But
I've been testing how many workers to run with, and I've noticed that
once I get above three workers, a couple of them get ballooning
virtual memory, jumping up to a little over 2GB. I initially thought
that the server was overloaded and swapping, but swap usage is still
0, and I get this behavior at over 50% free memory. It doesn't seem to
be causing performance problems, but I was wondering if anyone else
has observed this or similar behavior? I'm trying to decide if it's
normal or an item for concern.


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