From: khaines@...
Date: 2006-08-28T07:36:23+09:00
Subject: Mem leak without add_heap()?

Okay.  I went and did a little simple hacking on a 1.8.4 instance of Ruby 
to simply output to stdout some debugging info for various GC/memory 
related actions.

Using the info I gathered from that, I tuned a real application that I 
have which consistently leaks a small amount of RAM despite having no 
object leaks.  I have tested that by setting up a signal handler with 
which I can have it dump complete object counts at any time.  It grows 
slowly, but fairly deterministically.  Given a certain number of units of 
work that I ask of the code, RAM usage will increase a predictable amount, 
and never seems to go back down, even across very long runtimes (I 
recently killed and restarted some processes that had been running since 
sometime in 2005) but the object counts are the same.  So, that memory use 
is coming from somewhere else.

Anyway, but manually calling GC.start() at a modest interval within the 
application, I can prevent rb_newobj() from ever encountering an empty 
freelist and having to call garbage_collect() itself.  And by doing so the 
freed count stays very consistent and well above FREE_MIN, so add_heap is 
never invoked there.  I also put debugging output on each of the other two 
locations add_heap() can be called.  It never is.

However, despite this, RAM usage of the process continues to creep upward.
So.  Why?  A leak somewhere else, in some usage of 
rc_xmalloc/rb_xcalloc/rb_realloc?


Thanks,

Kirk Haines