From: "tmm1 (Aman Gupta)" Date: 2013-10-18T12:10:54+09:00 Subject: [ruby-core:57928] [ruby-trunk - Bug #9035][Open] [proposal] new RUBY_GC_HEAP_GROWTH_MAX_OBJ tuning parameter Issue #9035 has been reported by tmm1 (Aman Gupta). ---------------------------------------- Bug #9035: [proposal] new RUBY_GC_HEAP_GROWTH_MAX_OBJ tuning parameter https://bugs.ruby-lang.org/issues/9035 Author: tmm1 (Aman Gupta) Status: Open Priority: Normal Assignee: ko1 (Koichi Sasada) Category: core Target version: current: 2.1.0 ruby -v: ruby 2.1.0dev Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN = Background Currently, whenever the Ruby GC runs out of object slots the heap is grown by 1.8x (GC_HEAP_GROWTH_FACTOR). This works well for small programs, but given a large application it will cause rapid increase in memory. For example, if a ruby program is using 1 million objects and runs out of slots, it will grow to 1.8 million objects. This is a huge increase. = Proposal Introduce RUBY_GC_HEAP_GROWTH_MAX_OBJ to avoid exponential growth in larger ruby applications. After this limit is reached, heap growth will happen linearly instead of exponentially. For example, if growth_max=100k then the application above will grow from 1mm objects to 1.1mm objects. = Discussion RUBY_GC_HEAP_GROWTH_MAX can be represented either in a) bytesize, or b) number of objects. Arguments for (a) - more user friendly, since users are exposed primarily to RSS and want to control final RSS value - a bytesize based formula can include more varibles, for example the size of bitmaps associated with each RVALUE Arguments for (b) - consistent with existing tuning parameters (all object based, i.e. RUBY_HEAP_MIN_SLOTS) - GC tuning already requires measuring "startup objects", "objects per request", so object based is more friendly - bytesize is confusing because GROWTH_MAX only controls growth of ruby heap, not total RSS - this is an advanced feature meant for use by experts (default value will be 0 = no change from behavior) since experts will be using it, we can assume they have already measured the number of objects in their ruby app first -- http://bugs.ruby-lang.org/