Re: [ns2] Memory leak?

[kannan@catarina.usc.edu]

>>> From: "Christoph Haenle" <christoph@starburstcom.com>
>>> Date: Sat, 09 Aug 1997 00:19:00 EDT

Hi Chris,


> I've noticed a memory leak in ns-2.0b18 while monitoring memory usage with
> ps. It's ca. 500kB/min in my simulation. Also, I once got a core dump with
> 16MB, when my simulation crashed (due to insufficient memory? I checked the
> virtual memory and it was pretty exhausted at the time of the crash).
> 
> I use only Agent/TCP objects (ca. 150) with FTP as the traffic-source and
> SRM-agents. My scheduler is HEAP.
> 
> Has somebody got any suggestions where the leak comes from?

To the best of my knowledge, there are no memory leaks in my
version of SRM, and I suspect, very few in TCP :-)  I wanted to
check with some quick simulations before I answered; hence the
delay in my responding.

I expect you are using the stock SRM agent in the distribution,
with possibly minor mods?  You had mentioned at least 200 nodes
in your simulation in an earlier note.

	( If you are using the DV routing in the simulator, then
	there is a bug in memory allocation that I found after
	reading your note.  I am not sure if you are using
	dynamic routing though.  The fix for this is trivial,
	and will get into the current distrib later this week. )

The implementation is not optimised for memory yet (by design).
Each agent spins off a separate SRM/foo object to handle error
recovery for each loss, where foo is either request or repair.
The memory used by these objects is released by an agent, as
soon as its error recovery phase for that loss is complete.
But, if your loss rate is high, there can be issues in scaling.
So, questions:

	1.  How many sources?  What data rate?	2.  Do all the
	group members come on at the same time?  Or do
	    they come at different intervals?
	3.  Most importantly, what is your loss rate, and what
	is the
	    max. number of simultaneous loss you see?



Kannan