From: Joe Van Dyk <joevandyk@...>
Date: 2005-04-28T01:08:00+09:00
Subject: Re: memory leak

On 4/26/05, Joe Van Dyk <joevandyk@gmail.com> wrote:
> eek.  copy/paste borked.
> 
> See below for correct version.

FYI, you'll need SysVIPC installed
(http://deisui.org/~ueno/ruby/sysvipc.html).

In essence, the code below starts a thread that uses a object to read
from a message queue repeatedly.  If there's no messages left on the
message queue, the #recv method throws an exception, we catch that and
exit the loop.  The reader thread then sleeps for a second and reads
more messages from the queue.

The problem doesn't seem to be with the sending of the message over
the message queue, rather its the receive.  Somewhere, something isn't
being thrown away.  I used ObjectSpace to monitor the number of
objects that existed.  The total number of Objects in memory seem to
fluctuate, but don't increase over time (while memory is increasing).

I looked at the C code for the SysVIPC module but couldn't see any
obvious errors.

Any thoughts?

Joe

> On 4/26/05, Joe Van Dyk <joevandyk@gmail.com> wrote:
> > Got a memory leak in the following code.. not sure if DRb is necessary
> > in it or not.
> >
> > Put the code into a file named test.rb, btw.
> >
> > I think I tracked it down to the SystemVIPC::MessageQueue#recv method.
> >  If I don't give it a high receive length (like 8192), I don't see the
> > leak.  If I do give it a high length, the program takes up a very
> > large amount of space pretty quickly... about an increase of a meg
> > every five seconds.
> >
> > Any ideas?  (On my linux system, kernel.msgmax is set to 10000 if it matters)
> >
> 
> # test.rb
> 
> require 'drb'
> require 'sysvipc'
> 
> class Foo
>   def initialize
>     @key = SystemVIPC::ftok("test.rb", 1)
>     @msg = SystemVIPC::MessageQueue.new(@key, 0777 | SystemVIPC::IPC_CREAT)
>   end
> 
>   def recv
>     continue = true
>     while continue
>       begin
>         @msg.recv(1, 8192, SystemVIPC::IPC_NOWAIT)
>       rescue
>         continue = false
>       end
>     end
>   end
> 
>   def send
>     @msg.send(1, "HELLO WORLD HELLO WORLD")
>   end
> end
> 
> f = Foo.new
> some_thread = Thread.new(f) do |foo|
>   loop do
>     foo.recv
>     sleep 1
>   end
> end
> some_thread = Thread.new(f) do |foo|
>   loop do
>     foo.send
>     sleep 1
>   end
> end
> 
> DRb.start_service('druby://localhost:8000', f)
> DRb.thread.join
>