I am puzzled by the ruby's behavior and how it controls memory.
I understand the behavior of Ruby GC (primary or secondary) if the number of objects is counted above a threshold or limit (i.e. heap_available_slots, old_objects_limit, remembered_shady_object_limit, malloc_limit). Ruby starts / starts GC (primary or minor).
And after GC, if it cannot find enough memory, Ruby allocates (basically malloc, I assume) more memory for the current program.
In addition, this is a well-known fact that immediately frees up the RAM of the OS.
Now..
What I don’t understand is why Ruby releases memory (back to the OS) without running any GC.
Example
require 'rbtrace'
index = 1
array = []
while(index < 20000000) do
array << index
index += 1
end
sleep 10
print "-"
array=nil
sleep
. ruby 2.2.2p95.
htop RSS (test.rb PID 11483), 161 .
GC.stat ( rbtrace gem) ( GC count)
rbtrace -p 11843 -e '[Time.now,Process.pid,GC.stat]'
[Time.now,Process.pid,GC.stat]
=> [2016-07-27 13:50:28 +0530, 11843,
{
"count": 7,
"heap_allocated_pages": 74,
"heap_sorted_length": 75,
"heap_allocatable_pages": 0,
"heap_available_slots": 30162,
"heap_live_slots": 11479,
"heap_free_slots": 18594,
"heap_final_slots": 89,
"heap_marked_slots": 120,
"heap_swept_slots": 18847,
"heap_eden_pages": 74,
"heap_tomb_pages": 0,
"total_allocated_pages": 74,
"total_freed_pages": 0,
"total_allocated_objects": 66182,
"total_freed_objects": 54614,
"malloc_increase_bytes": 8368,
"malloc_increase_bytes_limit": 33554432,
"minor_gc_count": 4,
"major_gc_count": 3,
"remembered_wb_unprotected_objects": 0,
"remembered_wb_unprotected_objects_limit": 278,
"old_objects": 14,
"old_objects_limit": 10766,
"oldmalloc_increase_bytes": 198674592,
"oldmalloc_increase_bytes_limit": 20132659
}]
*** detached from process 11843
GC count => 7
25 . 6 , GC 7.
[Time.now,Process.pid,GC.stat]
=> [2016-07-27 14:16:02 +0530, 11843,
{
"count": 7,
"heap_allocated_pages": 74,
"heap_sorted_length": 75,
"heap_allocatable_pages": 0,
"heap_available_slots": 30162,
"heap_live_slots": 11581,
"heap_free_slots": 18581,
"heap_final_slots": 0,
"heap_marked_slots": 120,
"heap_swept_slots": 18936,
"heap_eden_pages": 74,
"heap_tomb_pages": 0,
"total_allocated_pages": 74,
"total_freed_pages": 0,
"total_allocated_objects": 66284,
"total_freed_objects": 54703,
"malloc_increase_bytes": 3248,
"malloc_increase_bytes_limit": 33554432,
"minor_gc_count": 4,
"major_gc_count": 3,
"remembered_wb_unprotected_objects": 0,
"remembered_wb_unprotected_objects_limit": 278,
"old_objects": 14,
"old_objects_limit": 10766,
"oldmalloc_increase_bytes": 198663520,
"oldmalloc_increase_bytes_limit": 20132659
}]
: , Ruby Release memory , GC. , .
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OS: OS X version 10.11.12