From: Adam Prescott <mentionuse@...>
Date: 2011-02-09T02:57:37+09:00
Subject: Re: Memory leak in 1.9.2-p330?

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On Tue, Feb 8, 2011 at 3:07 PM, Tal Yalon <tal.yalon@gmail.com> wrote:

> Hi all,
>
> Before I go and submit a bug report, I would appreciate a fresh pair of
> eyes
> hopefully finding a bug in the code and not in Ruby :)
>
> The code pushes elements to a "time window" queue of 2 seconds. Although I
> see that the maximum queue size stabilizes after a very short time (couple
> of seconds), the process's max RSS size starts to grow after a while 2
> minutes.
> Interestingly enough, the max RSS size stays fixed when running with 1.8.7.
> All tests were done on Ruby compiled using rvm.
>
> Printing the process's RSS and max RSS size was done to observe the leak in
> action, This code also leaks when removing the lines that execute ps and
> print it.
>
> Any idea will be welcomed.
>
> Thanks,
> Tal
>
> #!/usr/bin/env ruby
>
> before = Time.now.to_i
> i = 0
> max_rss = 0
> max_items = 0
>
> queue = []
> while true
>  now = Time.now.to_i
>  windows_start_time = now - 2
>  queue << now
>  while not queue.empty? and queue[0] < windows_start_time
>    queue.shift
>  end
>
>  if now - before >= 1
>    max_items = [ max_items, queue.size ].max
>    rss = `ps -o rss= -p #{Process.pid}`.to_i
>    max_rss = [ max_rss, rss].max
>    print("#{now} iters=#{i} queue_size=#{queue.size} rss=#{rss}, max:
> queue_size=#{max_items}, rss=#{max_rss}\n")
>    before = now
>  end
>  i += 1
> end
>

This is the error I was getting running your code:

/tmp/orig:8: [BUG] Segmentation fault
ruby 1.8.7 (2009-06-12 patchlevel 174) [universal-darwin10.0]

Abort trap

In 1.9 it was running fine, as you said.

I was having some trouble reading your code so I did some tidying to get
this:



time_to_print = Time.now

i = max_rss = max_items = 0

queue = []

while true
 start = Time.now
 interval = 2 # seconds

 queue << start

 while !queue.empty? && (Time.now - queue.first) > interval
   queue.shift
 end

 if Time.now - time_to_print >= 0
   max_items = [ max_items, queue.size ].max
   rss = `ps -o rss= -p #{Process.pid}`.to_i
   max_rss = [ max_rss, rss].max
   puts "#{start.to_i} iters=#{i} queue_size=#{queue.size} rss=#{rss} max
queue_size=#{max_items} rss=#{max_rss}"
   time_to_print = Time.now + 1
 end

 i += 1
end


The inner conditional chunk uses a Time.now in the comparison against
time_to_print, whereas before it hooked into now and before. It's also using
Time instances and not working off just integers.

However, this code now works fine on 1.8.7 and 1.9, for me.

Maybe this could highlight whatever is causing the bug in 1.8.7 in the
original code? Personally, I'm just more confused as to what might be
causing it!

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