Possible optimization of instance_variable_get ? #3419
Description
.@mrbrdo posed an interesting question in a comment to my meta programming benchmarking post about whether instance_variable get for strings/symbols could be optimized in the VM somehow.
Right now, according to my benchmark, it is about 3 times as slow to call instance_variable_get with a frozen string than it is to use the instance variable directly.
Benchmark code for direct reference:
class Test
def intitialize
@ivar = 'test'
end
def direct
@ivar
end
IVAR_NAME = "@ivar"
def hoist_ivar_name
instance_variable_get IVAR_NAME
end
def instance_variable_get_symbol
instance_variable_get :"@ivar"
end
def instance_variable_get_frozen
instance_variable_get('@ivar'.freeze)
end
def instance_variable_get_frozen_symbol
instance_variable_get('@ivar'.freeze.to_sym)
end
end
Benchmark.ips do |benchmark|
instance = Test.new
benchmark.report("direct") {instance.direct}
benchmark.report("hoist_ivar_name") {instance.hoist_ivar_name}
benchmark.report("ivar get symbol") {instance.instance_variable_get_symbol}
benchmark.report("ivar get frozen") {instance.instance_variable_get_frozen}
benchmark.report("ivar get frozen sym") {instance.instance_variable_get_frozen_symbol}
endResults with JRuby 9.0.0.3:
tobi@airship ~ $ ruby ivar_get.rb
Calculating -------------------------------------
direct 150.109k i/100ms
hoist_ivar_name 140.955k i/100ms
ivar get symbol 192.115k i/100ms
ivar get frozen 158.494k i/100ms
ivar get frozen sym 148.150k i/100ms
-------------------------------------------------
direct 10.335M (±22.3%) i/s - 48.185M
hoist_ivar_name 4.713M (±28.6%) i/s - 21.425M
ivar get symbol 8.628M (±27.8%) i/s - 39.191M
ivar get frozen 3.109M (± 4.7%) i/s - 15.532M
ivar get frozen sym 5.500M (±15.0%) i/s - 26.519M
tobi@airship ~ $ ruby --server -Xcompile.invokedynamic=true ivar_get.rb
Calculating -------------------------------------
direct 91.369k i/100ms
hoist_ivar_name 112.476k i/100ms
ivar get symbol 113.564k i/100ms
ivar get frozen 160.592k i/100ms
ivar get frozen sym 158.691k i/100ms
-------------------------------------------------
direct 10.812M (±19.7%) i/s - 50.162M
hoist_ivar_name 5.402M (±28.8%) i/s - 24.070M
ivar get symbol 10.310M (±12.7%) i/s - 49.968M
ivar get frozen 3.163M (± 5.0%) i/s - 15.899M
ivar get frozen sym 5.428M (±17.5%) i/s - 26.025M
Thanks for all your work, my original got faster thanks to Jruby 9.0.3.0 :)
Tobi