Bug #11101

Forking is killing my memory when running GC

Added by tkalmus (Thomas Kalmus) almost 5 years ago. Updated 9 months ago.

Target version:


Memory is duplicated when forking and calling GC in 2.2.1. The main issue here is that we are operating with huge data, going up to 3GB, and one fork is enough to kill our machine.

We have written a small program that reproduces the issue (see attached file).

The program instantiates an object and then forks into two processes.
The GC is called in the child process.
The memory allocation (as given by /proc/pid/smaps) changes from shared to private, thereby indicating a doubling of memory consumption.

Here is the output of the program (size is in mb):

ruby version 2.1.3
time pid message shared private
4.011s 4723 Parent pre GC 68 0
4.013s 4737 Child pre GC 68 0
8.019s 4723 Parent post GC 5 62
8.093s 4737 Child post GC 5 66

We have tested the program on Ubuntu 14.04 with ruby 1.9.3 and 2.2.1. The tests have been performed on a freshly installed Ubuntu machine.

We have also tried to fork 10 children and see a 10 doubling of the memory consumption, the issue only occurs after running the GC.


mem.rb (1.25 KB) mem.rb tkalmus (Thomas Kalmus), 04/27/2015 03:13 PM

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