[tlug] Process Memory Usage

[Curt Sampson <cjs@example.com>]

I notice that the VM size of processes under Linux, as compared
to NetBSD, is remarkably large. I suspect some sort of accounting
difference, but that's not the real issue here.

I'm dealing with machines where memory's getting a bit tight. Generally
we've got about 550 processes running, most of which are a couple of
daemons (200-300 of each), one written in Perl, and the other in Ruby.
Overall, memory usage is about 6-7 GB, outside of buffer cache.

Obviously these processes have a lot of common code, and the the VM size
from /proc/$pid/status (this is the figure also reported by ps and top)
is obviously fairly useless. (The last time I had a look, 250 instances of
that perl daemon alone had a VM usage figure that summed to about 45 GB.)

So what I want to know is, where do I get the figure for the size of
non-shared memory that is backed by swap? That is, I don't care about
the executable itself, nor the shared libs, nor mmapped files, just the
memory that would actually be freed if I killed the process.

And guidance on where to go to find out more about the details of
process memory allocation in Linux is welcome.

cjs
-- 
Curt Sampson       <cjs@example.com>        +81 90 7737 2974   
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